Ddl commands - Data Integrity Preservation: DDL commands maintain data integrity by enforcing constraints and ensuring data consistency within the database. Performance …

 
Jun 5, 2023 · MySQL Cheat Sheet. MySQL is a popular open-source relational database management system known for its ease of use and scalability. Sometimes, you will need a little help while working on a project. That's why we created this MySQL Cheat Sheet. Instructions for installing MySQL are available at: https://dev.mysql.com.. Brightstar login mobile

Google Home is a voice-activated assistant that can help you control your home. Google Home is a voice-activated assistant that can help you control your home. Using it is simple —...Oct 12, 2023 · SQL provides a rich and powerful set of commands for working with databases, and one crucial aspect of SQL is the Data Definition Language (DDL). … Data Definition Language (DDL) is a standard for commands that define the different structures in a database. DDL statements create, modify, and remove database objects such as tables, indexes, and users. Common DDL statements are CREATE, ALTER, and DROP. Click Utilities. Click Generate DDL. The Generate DDL page appears. The Generate DDL Wizard appears. Select a database schema and click Next. Output - Specify an output format. Select either Display Inline or Save As Script File. Check All - Select this option to include all object types for which to generate DDL. Object Type - Select the ...Nov 15, 2023 · Querying data commands are SQL statements used to retrieve data from a database. Here are the main Querying Data commands: 1. SELECT Statement. The SELECT statement is the primary command used to retrieve data from a database. It allows you to specify which columns you want to retrieve and from which table.May 4, 2023 · A Beginner’s Guide to SQL Commands: DDL, DML, DCL, & TCL. The Structured Query Language (SQL), as we all know, is a database language that allows us to execute specific operations on existing databases as well as construct new databases. To complete the tasks, SQL employs commands such as Create, Drop, and Insert. 9.2.1 DDL Commands. We will illustrate three DDL commands (create table, alter table, create index) as we create tables and modify tables using the Library database. Figure 9.4 Data Definition Commands. In some database environments, we can run more than one command at a time. The commands would be located in a file and would be submitted as a ... Feb 21, 2024 · These languages have different functions: DDL is used for working on the relational database structure, whereas DML is used to work with the data stored in the relational database. Most DBMSs use structured query language (SQL) for both data definition and data manipulation. SQL was developed in the 1970s and since then it has …1 day ago · W3Schools Spaces is a website-building tool that enables you to create and share your website. In addition to a server, you get a SQL Database where you can store and access your data. It's easy to use and doesn't require any setup. The code editor is packed with features to help you achieve more: Templates: Start from scratch or use a …Sep 20, 2023 · SQL Truncate. SQL Truncate is one of the Data Definition Language (DDL) commands. It deletes all the records in a database table. However, it does not delete the table’s structure; instead, it simply reconstructs the structure. The table’s original structure is retained while all the records are removed. Because it reconstructs the ...Mar 5, 2019 ... ... commands 0:49 - DDL commands 3:28 - DML commands 5:00 - DCL commands 6:11 - TCL commands 8:34 - Constraints ▻ Database Management System ...Mar 7, 2024 · DML for Tutorial Examples. DML stands for Data Manipulation Language. These are the INSERT statements that you will need to run in your database to populate the data: Execute the following DML statements in your database: INSERT INTO categories. (category_id, category_name) VALUES. (25, 'Deli');Feb 12, 2015 · DDL: Stands for "Data Definition Language." A DDL is a language used to define data structures and modify data . For example, DDL commands can be used to add, remove, or modify tables within in a database . DDLs used in database applications are considered a subset of SQL , the Structured Query Language. However, a DDL may also … There are five types of SQL commands: DDL, DML, DCL, TCL, and DQL. 1. Data Definition Language (DDL) DDL changes the structure of the table like creating a table, deleting a table, altering a table, etc. All the command of DDL are auto-committed that means it permanently save all the changes in the database. Here are some commands that come ... Feb 10, 2022 · The operations for which privileges may be granted to or revoked from a user or role apply to both the Data definition language (DDL) and the Data manipulation language (DML), and may include CONNECT, SELECT, INSERT, UPDATE, DELETE, EXECUTE and USAGE. In the Oracle database, executing a DCL command issues an implicit commit. Jul 9, 2012 · 4. at most pages I have read that "DDL commands have AutoCommit in SQL Server", if I am not wrong this statement simply means that we don't need explicit commit command for DDL commands. then why... 1) Alter TABLE EMP Add Age INT; UPDATE EMP SET Age=20; fails ,saying Invalid column name 'Age'. 2) BEGIN TRAN Alter TABLE EMP Add Age INT; ROLLBACK. Jun 5, 2023 · MySQL Cheat Sheet. MySQL is a popular open-source relational database management system known for its ease of use and scalability. Sometimes, you will need a little help while working on a project. That's why we created this MySQL Cheat Sheet. Instructions for installing MySQL are available at: https://dev.mysql.com.Sep 5, 2023 ... 1. PRIMARY KEY. Within any database ensuring data accuracy and consistency is key. A powerful tool for achieving this goal is the PRIMARY KEY ...In SQL, Data Definition Language (DDL) shapes the database structure through commands like CREATE and ALTER, whereas Data Manipulation Language (DML) ...Learn the basics of SQL commands, the database language used to perform various operations on data and database structures. Find out the syntax and examples of DDL, DQL, DML, DCL and TCL commands and their categories. See moreMar 5, 2017 · DDL Commands in SQL Examples: CREATE – Creates objects e.g. table in the database. ALTER – Alters objects of the database. e.g. modifying a column of a table. DROP – Deletes objects from the database. e.g. remove table from a sql database. TRUNCATE – Deletes all records from a table and resets table identity to initial value. Feb 22, 2024 · Some typical DDL commands are CREATE, ALTER, DROP, TRUNCATE, and RENAME. DDL Command Examples. 1. CREATE - This command is used to create a new table in the database.Oct 24, 2017 ... I'd like to run a command in my deployment pre-start hooks which deletes the public schema in the database and then re-creates it before ...Mar 10, 2023 · Introduction to SQL DDL Commands. Data Definition Language or DDL commands in standard query language (SQL) are used to describe/define the database schema. These commands deal with database schema creation and its further modifications. Some popularly known DDL commands are CREATE, ALTER, DROP, TRUNCATE, and COMMENT. Mar 3, 2024 · DCL, or Data Control Language, plays a pivotal role in managing database security through permissions. While DDL, DML, and DQL deal with the structure, manipulation, and querying of data, respectively, DCL focuses on who can do what within a database. Mastering DCL commands like GRANT and REVOKE is crucial for any database administrator or ... Dec 31, 2016 · DDL is short name of Data Definition Language, which deals with database schemas and descriptions, of how the data should reside in the …Dec 28, 2023 · Types of DDL Commands. The DDL Commands are as follows - CREATE Command: This command creates databases or tables in RDBMS. DROP Command: This command can delete a column or drop the whole database from RDBMS. ALTER TABLE Command: This command can be used to add new columns. Drop command and Rename also work along with this command. Learn the basics of SQL commands, the database language used to perform various operations on data and database structures. Find out the syntax and examples of DDL, DQL, DML, DCL and TCL commands and their categories. See more5 days ago · DDL commands are usually executed in a SQL browser or stored procedure. DDL is contrasted with Data Manipulation Language (DML) which is the SQL that is used to actually access and manipulate data in database objects. The majority of data analysts will rarely execute DDL commands and will do the majority of their work creating DML …Feb 22, 2024 · Some typical DDL commands are CREATE, ALTER, DROP, TRUNCATE, and RENAME. DDL Command Examples. 1. CREATE - This command is used to create a new table in the database.Jan 10, 2024 · 1. CREATE. The `CREATE` command is fundamental for establishing the foundation of a database by creating tables, schemas, or indices. Below is the …Jul 9, 2012 ... In autocommit mode, it sometimes appears as if an instance of the Database Engine has rolled back an entire batch instead of just one SQL ...db2look -d department -e -t tab1 "\"My TaBlE2\"" -o db2look.sql. Generate the DDL statements for all objects (federated and non-federated) in the federated database FEDDEPART. For federated DDL statements, only those that apply to the specified wrapper, FEDWRAP, are generated. The output is sent to standard output.Sep 27, 2022 · DDL commands cannot be rolled back, as they include a COMMIT as part of their execution. This is an important point to remember, especially if the statements in the transaction may be required to be rolled back. This includes the TRUNCATE command, which is similar to the DELETE command. 9.2.1 DDL Commands. We will illustrate three DDL commands (create table, alter table, create index) as we create tables and modify tables using the Library database. Figure 9.4 Data Definition Commands. In some database environments, we can run more than one command at a time. The commands would be located in a file and would be submitted as a ... Mar 15, 2022 · The DDL instructions are used to create the database or schema, whereas the DML commands are used to populate and change it. DDL instructions have the ability to affect the whole database or table, whereas DML statements only affect single or multiple rows dependent on the query condition. Modifications to DDL instructions are permanent and ... Jun 26, 2015 · इसके अलावा DDL का इस्तेमाल metadata की जानकारी को स्टोर करने के लिए भी किया जाता है. नीचे आपको महत्वपूर्ण DDL commands दी गयी हैं:-1.The rest of the DDL commands targeting the same table are blocked until CREATE INDEX is in progress. DML command execution is not affected and can be performed in parallel. Schema changes applied by this command are persisted on disk if Ignite persistence is enabled. Thus, the changes can survive full cluster restarts.May 18, 2023 ... In short, DDL commands are used to define the structure of tables, and DML is used to modify the data in the table. Both commands enable easier ...The DDL commands in SQL Server that can be used to define the database schema are part of DDL or Data Definition Language. It is used to create and modify the structure of database objects and only deals with schema descriptions. DDL commands is a set of SQL commands that only allow for creating, modifying, and deleting database structures, not ...Returns a DDL statement that can be used to recreate the specified object. For databases and schemas, GET_DDL is recursive (i.e. it returns the DDL statements for recreating all supported objects within the specified database/schema). GET_DDL currently supports the following object types: Alerts (see CREATE ALERT)A DDL full form is Data Definition Language,” which is a part of DBMS and a subset of SQL. There are basically 4 commands in the DDL command: create, alter, drop, and truncate. What is the purpose of the data definition language? DDL is used to create, modify, and remove the structure of database objects in a database, such as the creation ...Oct 3, 2023 · Syntax: TRUNCATE is a DDL (Data Definition Language) command and is used to delete all the rows or tuples from a table. Unlike the DELETE command, the TRUNCATE command does not contain a WHERE clause. In the TRUNCATE command, the transaction log for each deleted data page is not recorded. Unlike the DELETE …DDL statements are SQL statements that are used to define the data structure in a database (DDL = Data Definition Language). In the SAP MaxDB database system, DDL statements are controlled by the transaction concept. After a DDL statement has been completed with a COMMIT, it can no longer be undone. More Information. SQL Reference Manual, Data ...5 days ago · DDL commands are usually executed in a SQL browser or stored procedure. DDL is contrasted with Data Manipulation Language (DML) which is the SQL that is used to actually access and manipulate data in database objects. The majority of data analysts will rarely execute DDL commands and will do the majority of their work creating DML …Oct 12, 2022 · DDL commands. DDL stands for Data Definition Language. It includes the set of commands that you use to perform various tasks related to data definition. You use these commands to specify the structure of the storage and methods through which you can access the database system. You use DDL commands to perform the following functions: INSERT (id, value) VALUES (S.id, S.value); These are the fundamental SQL DML statements used for querying and manipulating data within a relational database. They allow you to interact with data, retrieve information, insert new records, update existing records, and delete unwanted data, making SQL a versatile language for managing database ... The DDL commands in SQL are used to create database schema and to define the type and structure of the data that will be stored in a database. SQL DDL …To manage relational databases efficiently, DDL Commands in SQL are indispensable in defining or changing database objects. The comprehensive nature of this guide highlights key functions of the commonly used DDL commands. This includes creating tables along with modifying them or even adding indices. Also covered are creating views or schemas ...DDL commands are used to create, manipulate, and modify objects in Snowflake, such as users, virtual warehouses, databases, schemas, tables, views, columns, functions, and stored procedures. They are also used to perform many account-level and session operations, such as setting parameters, initializing variables, and initiating transactions.The Ten Commandments are a set of biblical principles that outline instructions on ethics and worship practices in the Jewish and Christian religions. The Ten Commandments deal wit...Feb 14, 2024 · DDL Commands in SQL. DDL commands in SQL are used to create, change, or delete the design of a database. These commands include: CREATE: Builds new database objects such as tables, indexes, or views. ALTER: Modifies existing database objects, allowing changes to their structure. DROP: Deletes database objects, removing them from the database ... This quiz/worksheet is a simple tool you can use to measure your comprehension of DDL commands. The questions within look at what these commands are used for as ...4 days ago · Database Commands. All command documentation outlined below describes a command and its available parameters and provides a document template or prototype for each command. Some command documentation also includes the relevant mongosh helpers. To run a command against the current database, use db.runCommand ():DDL commands are used to create, manipulate, and modify objects in Snowflake, such as users, virtual warehouses, databases, schemas, tables, views, columns, functions, and stored procedures. They are also used to perform many account-level and session operations, such as setting parameters, initializing variables, and initiating transactions.Feb 22, 2024 · Some typical DDL commands are CREATE, ALTER, DROP, TRUNCATE, and RENAME. DDL Command Examples. 1. CREATE - This command is used to create a new table in the database.Feb 22, 2024 · Some typical DDL commands are CREATE, ALTER, DROP, TRUNCATE, and RENAME. DDL Command Examples. 1. CREATE - This command is used to create a new table in the database.May 17, 2020 ... This is a tutorial on different types of Data Definition Language (DDL) Commands in SQL. Every command is shown with its syntax and ...It might sound like its own programming language, but data definition language (DDL) is really a way to view certain SQL commands. These are commands that are used to modify the structure of a ...Sep 20, 2023 · SQL Truncate. SQL Truncate is one of the Data Definition Language (DDL) commands. It deletes all the records in a database table. However, it does not delete the table’s structure; instead, it simply reconstructs the structure. The table’s original structure is retained while all the records are removed. Because it reconstructs the ...Jul 15, 2022 · SQL commands divided into 5 subgroups — Source: Author. As you can tell, the Data Definition Language (DDL) and Data Manipulation Language (DML) are the two biggest sub-categories when it comes to grouping together SQL commands. On the one hand the DDL commands are mostly used to change the schema of a database whilst …In SQL, there are mainly three types of commands - DDL - which stands for Data Definition Language which comprises SQL commands used for defining the database which includes creating tables, providing specifications, modifying tables and so on. Examples of DDL include CREATE, DROP, ALTER, etc. The changes that are caused by issuing DDL …Sep 27, 2021 · An Introduction To SQL Commands: DDL, DML, DCL, and TCL. SQL is the Structured Query Language used to store, manipulate, and retrieve data present in a database server. MySQL is a relational database management system. It supports large databases and is customizable. This article will discuss the important commands in SQL.Unity of command is a military principle that has been applied to business. It follows the idea that a subordinate should have only one person to whom they are directly responsible...The ALTER command is a DDL command to modify the structure of existing tables in the database by adding, modifying, renaming, or dropping columns and constraints. Use the ALTER TABLE RENAME command to rename column names. Syntax: ALTER TABLE table_name RENAME COLUMN old_column_name TO new_column_name;The 10 Commandments are biblical precepts issued to Moses on Mount Sinai and are considered to be divinely inspired, according to Judaism, Catholicism and other Christian denominat...May 29, 2023 · CBSE Class 12 Sample Paper for 2022 Boards [Term 2] - Computer Science. Categorize following commands into DDL and DML commands?INSERT INTO, DROP TABLE, ALTER TABLE, UPDATE...SETAnswerDDL: DROP TABLE, ALTER TABLEDML: INSERT INTO, UPDATE. .. SET.DDL Commands DATA DEFINITION LANGUAGE (DDL): The Data Definition Language (DDL) is used to create and destroy databases and database objects. SQL: create command create is a DDL SQL command used to create a table or a database in relational database management system. Creating a Database To create a database in RDBMS, create …DDL – Data Definition Language. DML – Data Manipulation Language. DDL is to define and DML is to manipulate. These are the main important distinctions when remembering how they differ. We can use DDL to define or modify an object. On the other hand DML is used for manipulating data within objects.Feb 10, 2024 · DDL(Data Definition Language): To make/perform changes to the physical structure of any table residing inside a database, DDL is used. These commands when executed are auto-commit in nature and all the changes in the table are reflected and saved immediately. DML(Data Manipulation Language): Once the tables are created and the database is ... Sep 27, 2022 · The DDL commands CREATE, ALTER, and DROP require exclusive access to the object you’re working on. However, the GRANT, REVOKE, ANALYZE, and AUDIT commands do not. SQL Developer includes a setting for autocommit, or automatically committing statements. You can find out more about that and how to view and change it …Feb 16, 2023 · What Does DDL Do? Data Definition Language is a subset of SQL that is used to define the structure of a database. It is used to create, alter, and delete database objects such as tables, views, indexes, and stored procedures. DDL statements can also be used to define the relationships between different tables in the database.Jun 25, 2020 · DDL (Data Definition Language) commands are a subset of SQL used to define and modify various data structures. This group includes commands designed to create, modify and delete various database objects. Commands CREATE (creation), ALTER (modification) and DROP (deletion) have most types of database objects (tables, views, procedures, triggers ... Click Utilities. Click Generate DDL. The Generate DDL page appears. The Generate DDL Wizard appears. Select a database schema and click Next. Output - Specify an output format. Select either Display Inline or Save As Script File. Check All - Select this option to include all object types for which to generate DDL. Object Type - Select the ...Feb 21, 2024 · These languages have different functions: DDL is used for working on the relational database structure, whereas DML is used to work with the data stored in the relational database. Most DBMSs use structured query language (SQL) for both data definition and data manipulation. SQL was developed in the 1970s and since then it has …Jul 15, 2022 · SQL commands divided into 5 subgroups — Source: Author. As you can tell, the Data Definition Language (DDL) and Data Manipulation Language (DML) are the two biggest sub-categories when it comes to grouping together SQL commands. On the one hand the DDL commands are mostly used to change the schema of a database whilst the commands belonging ... Apr 26, 2023 ... Hive DDL Commands Explained with Examples · CREATE DATABASE IF NOT EXISTS emp; · CREATE DATABASE temp LOCATION '/project/hive/warehouse'; &mi...Feb 28, 2023 · In this post, we will introduce some common commands for managing table schemas in MySQL, with a focus on the convention and best practices for each operation. It can work as a handbook (with necessary adjustments) for new data engineers. ... The data definition language (DDL) query for an existing table can be found by this command:Jan 22, 2024 · 事件触发器行为总览 事件触发器触发矩阵 事件触发器函数 在命令结束处捕捉更改 处理被DDL命令删除的对象 处理表重写事件 反解析DDL命令 Redrock Postgres 提供了事件触发器。和常规触发器(附着在一个表上并且只捕捉DML事件)不同,事件触发器对一个特定数据库来说是全局的,并且可以捕捉DDL事件 ...Learn the basics of SQL commands, the database language used to perform various operations on data and database structures. Find out the syntax and examples of DDL, DQL, DML, DCL and TCL commands and their categories. See moreApr 12, 2021 · 本节的函数,用来从事件触发器中检索信息。1、捕获命令结尾的改变 pg_event_trigger_ddl_commands返回通过每个用户操作执行的DDL命令列表,当调用函数中ddl_command_end事件触发器,如果在任何其它上下文中调用,则抛出一个错误。pg_event_trigger_ddl_commands返回每个基本执行命令的每一行,单独SQL语句的命 …Aug 25, 2023 · Data Definition Language (DDL) refers to the CREATE, ALTER and DROP statements. DDL or Data Definition Language actually consists of the SQL commands that can be used to define the database schema. DDL allows to add / modify / delete the logical structures which contain the data or which allow users to access / maintain the data …In SQL, there are mainly three types of commands - DDL - which stands for Data Definition Language which comprises SQL commands used for defining the database which includes creating tables, providing specifications, modifying tables and so on. Examples of DDL include CREATE, DROP, ALTER, etc. The changes that are caused by issuing DDL … SQL Command Reference. These topics provide reference information for all the Snowflake SQL commands (DDL, DML, and query syntax). Query Syntax — structure of SQL queries in Snowflake. Query Operators — arithmetic, logical, and other types of operators. DDL (Data Definition Language) Commands — overview of DDL commands.

Mar 18, 2024 · Below are the major steps we will perform to complete this task: Create a new table that will hold the audit data. Create a DDL trigger that will …. Best android antivirus software

ddl commands

DDL Commands DATA DEFINITION LANGUAGE (DDL): The Data Definition Language (DDL) is used to create and destroy databases and database objects. SQL: create command create is a DDL SQL command used to create a table or a database in relational database management system. Creating a Database To create a database in RDBMS, create …Jun 5, 2020 ... (Reg_no varchar2(10), Name char(30), DOB date, Address varchar2(50));. TRUNCATE Command.DDL-related commands. ADMIN SHOW DDL : Used to view the status of TiDB DDL operations, including the current schema version number, the DDL ID and address of ...Sep 10, 2019 · SQL commands are instructions, coded into SQL statements, which are used to communicate with the database to perform specific tasks, work, functions and queries with data. SQL commands are mainly divided into four major categories based on their functionality. Data Definition language (DDL) Data Manipulation language (DML)In SQL, there are mainly three types of commands - DDL - which stands for Data Definition Language which comprises SQL commands used for defining the database which includes creating tables, providing specifications, modifying tables and so on. Examples of DDL include CREATE, DROP, ALTER, etc. The changes that are caused by issuing DDL …Icml 2024 Ddl Commands. Both iclr and neurips have such processes, so they should be. Tue mar 26th 2024 04:59:59 pdt. Following are the five ddl commands in sql: Jul 21st through sat the 27th, 2024 at the messe wien exhibition congress center. Along With Neurips And Iclr, It Is One Of The. The icmlEXPERIMENT 2 · AIM: To execute the queries in DDL commands. · CREATE TABLE<tablename> (column_1 datatype(size), column_2 datatype(size)… · Syntax to alte...Jul 15, 2022 · SQL commands divided into 5 subgroups — Source: Author. As you can tell, the Data Definition Language (DDL) and Data Manipulation Language (DML) are the two biggest sub-categories when it comes to grouping together SQL commands. On the one hand the DDL commands are mostly used to change the schema of a database whilst the commands belonging ... Apache HBase DDL Commands. HBase - Basic Commands · HBase - DML Commands · 1. Create Table. Using create table command we can create a table by specifying the .....A DDL full form is Data Definition Language,” which is a part of DBMS and a subset of SQL. There are basically 4 commands in the DDL command: create, alter, drop, and truncate. What is the purpose of the data definition language? DDL is used to create, modify, and remove the structure of database objects in a database, such as the creation ...It might sound like its own programming language, but data definition language (DDL) is really a way to view certain SQL commands. These are commands that are used to modify the structure of a ...Dec 8, 2020 · What are the differences between DDL and DML in DBMS?, DDL is used for describing the structure of a database whereas DML is used for modifying and fetching data from a database. The commands under DDL are Create, Drop, Truncate, Alter and Rename. The commands under DDL are Select, Update, Delete and Insert. The DDL commands … INSERT (id, value) VALUES (S.id, S.value); These are the fundamental SQL DML statements used for querying and manipulating data within a relational database. They allow you to interact with data, retrieve information, insert new records, update existing records, and delete unwanted data, making SQL a versatile language for managing database ... Apr 10, 2023 · The DDL commands in SQL are used to specify the kind and structure of the data that will be stored in a database and to establish database schema. DDL Commands is used for establishing new tables, indexes, sequences, stogroups, etc. and for defining the features of these objects, such as data type, field length, and alternative table names.May 24, 2023 · The DDL commands work with the SQL query statements, executed to perform and show desired results. Once queried and run, the DDL commands cannot be rolled back and do commit implicitly. Tables are the database objects that store the data records. These data interact with other table data and form a relation at a structural level.Oct 13, 2023 ... Data Manipulation Language (DML · Data are inserted into tables using INSERT. · A table's existing data is updated using UPDATE. · Delete&...Mar 18, 2024 · Below are the major steps we will perform to complete this task: Create a new table that will hold the audit data. Create a DDL trigger that will …Oct 13, 2023 ... Data Manipulation Language (DML · Data are inserted into tables using INSERT. · A table's existing data is updated using UPDATE. · Delete&...Mar 5, 2024 · Popular DDL Commands with Examples. When you work with any database, you’ll encounter the need to manage data objects (e.g. tables, stored …Jan 2, 2023 · 当在一个ddl_command_end事件触发器的函数中调用时, pg_event_trigger_ddl_commands返回被每一个用户动作 执行的DDL命令的列表。如果在其他任何环境中 调用这个函数,会发生错误。 pg_event_trigger_ddl_commands为每一个被执行的基本 命令返回一行,某些只有一个单一 SQL 句子的命令可能会返回多于一行。.

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