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  • delete sql语句
    千次阅读
    2022-03-11 20:34:31

    SQL之delete语句

    DELETE 语句用于删除表中的记录。

    SQL语法

    delete from 表名 where 列名="value ";

    delete from table_name
    where some_column = some_value;
    

    :SQL DELETE语句中的where子句!where子句规定哪条记录或者哪些记录要被删除!

    SQL DELETE实例

    假设我们要从 “student” 表中删除姓名为 “张三” 且国家为 中国的学生信息。

    我们使用下面的 SQL 语句:

    delete from student where name = '张三' and country = '中国';
    

    删除所有数据

    你可以在不删除表的情况下,删除表中所有的行(数据)。这意味着表结构、属性、索引将保持不变:

    delete from table_name;
    或者
    truncate table table_name;(Mysql快速清空数据)
    

    清空表数据的常见种方式

    1、truncate–删除所有数据,保留表结构,不能撤销还原

    2、delete–是逐行删除速度极慢,不适合大量数据删除

    3、drop–删除表,数据和表结构一起删除

    sql练习网站推荐:LintCode 炼码

    更多相关内容
  • SQL Delete语句

    2021-02-01 18:45:30
    在本教程中,您将学习如何使用SQL DELETE语句删除表中的一行或多行。1. SQL DELETE语句简介要从表中删除一行或多行,请使用DELETE语句DELETE语句的一般语法如下:DELETEFROMtable_nameWHEREcondition;首先,提供...

    在本教程中,您将学习如何使用SQL DELETE语句删除表中的一行或多行。

    1. SQL DELETE语句简介

    要从表中删除一行或多行,请使用DELETE语句。 DELETE语句的一般语法如下:

    DELETE

    FROM

    table_name

    WHERE

    condition;

    首先,提供要删除行的表名称(table_name)。

    其次,在WHERE子句中指定条件以标识需要删除的行记录。 如果省略WHERE子句,则将删除表中的所有行记录。 因此,应始终谨慎使用DELETE语句。

    一般来说,DELETE语句不会将结果集。 但是,它只返回已删除的行数。

    2. SQL DELETE语句示例

    我们将使用employees和dependents表来演示DELETE语句。

    9c77e3138520657628783829c879e386.png

    2. SQL删除表中的一行

    使用以下DELETE语句从dependents表中删除ID为:16的行记录。

    DELETE FROM dependents

    WHERE

    dependent_id = 16;

    由于WHERE子句包含主键表达式,因此DELETE语句只删除一行。可以使用以下语句验证是否已删除dependents中ID为:16的行记录:

    SELECT

    COUNT(*)

    FROM

    dependents

    WHERE

    dependent_id = 16;

    3. SQL DELETE多行示例

    要删除表中的多个行记录,请使用WHERE子句中的条件来选择要删除的行记录。 例如,以下语句使用IN运算符来删除dependents表中id为100,101或102的信息。

    DELETE FROM dependents

    WHERE

    employee_id IN (100 , 101, 102);

    4. SQL DELETE来自相关表的行

    一名员工可能有零个或多个家属,而一个受抚养人只属于一名员工。 dependents表中的employee_id列链接到employees表中的employee_id列。

    员工与家属表之间的关系是一对多的。

    从逻辑上讲,如果不引用员工,就不能存在依赖关系。 换句话说,当删除员工信息时,他/她的家属也必须要删除。

    例如,要删除员工ID为199和所有员工的依赖项,需要执行两个DELETE语句,如下所示:

    DELETE

    FROM

    employees

    WHERE

    employee_id = 199;

    DELETE

    FROM

    dependents

    WHERE

    employee_id = 199;

    大多数数据库系统都支持外键约束,因此当删除表中的一行时,外键表中的行也会自动删除。

    因此,执行以下DELETE语句时:

    DELETE

    FROM

    employees

    WHERE

    employee_id = 199;

    在执行上面语句后,employee_id为199的所有行也会自动删除。

    要更有效地从表中删除所有行,可以使用TRUNCATE TABLE语句,而不是使用不带WHERE子句的DELETE语句。

    通过上面的示例和学习,您应该了解SQL DELETE语句用法,以及如何应用它来删除表中的一行或多行。

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  • sql delete语句_SQL Delete语句概述

    千次阅读 2020-07-25 13:57:24
    sql delete语句 This article on the SQL Delete is a part of the SQL essential series on key statements, functions and operations in SQL Server. 有关SQL Delete的这篇文章是有关SQL Server中关键语句...

    sql delete语句

    This article on the SQL Delete is a part of the SQL essential series on key statements, functions and operations in SQL Server.

    有关SQL Delete的这篇文章是有关SQL Server中关键语句,函数和操作SQL基本系列的一部分。

    To remove a row from a table is accomplished through a Data Manipulation Language, aka DML statement, using the delete keyword. The SQL delete operation is by far the simplest of all the DML commands. On execution of the delete command, we don’t have to worry about getting any form of data from the table, and we don’t have to worry about working with any data that we get back from the table(s). We just simply tell the database to delete a specific record, and it either does or it doesn’t. It’s that simple.

    从表中删除行是通过数据操作语言(又称DML语句)使用delete关键字完成的。 到目前为止,SQL删除操作是所有DML命令中最简单的操作。 在执行delete命令时,我们不必担心从表中获取任何形式的数据,也不必担心处理从表中获取的任何数据。 我们只是简单地告诉数据库删除特定记录,它要么执行,要么不执行。 就这么简单。

    First, let’s quickly review what an SQL delete statement looks like. We need to tell the database and table from where it should delete the data. It’s a good idea to add a condition clause to set the scope of data deletion. Otherwise, it will delete everything in the table.

    首先,让我们快速回顾一下SQL delete语句的外观。 我们需要告诉数据库和表应从何处删除数据。 添加条件子句以设置数据删除的范围是一个好主意。 否则,它将删除表中的所有内容。

    Let’s take a look at our table and removing some records.

    让我们看一下表并删除一些记录。

    如何删除不带where子句的行 (How to delete rows with no where clause)

    The following example deletes all rows from the Person.Person the table in the AdventureWorks2014 database. There is no restriction enforced on the SQL delete statement using a WHERE clause.

    下面的示例从AdventureWorks2014数据库中的Person.Person表中删除所有行 。 使用WHERE子句SQL delete语句没有任何限制。

    USE Adventureworks2014;
    GO
    DELETE FROM [Person].[Person];
    

    如何使用where子句删除行 (How to delete rows with where clause)

    The following example deletes rows from the [Person].[Person] table in the AdventureWorks2014 database in which the value in the businessEntityID column is greater than 30,000

    以下示例从AdventureWorks2014数据库的[Person]。[Person]表中删除行,其中businessEntityID列中的值大于30,000

    USE Adventureworks2014;
    GO
    DELETE FROM [Person].[Person]
    WHERE businessEntityID > 30000;
    

    Note: An unfortunate mistake that may occur is to accidently run a SQL Delete with no Where clause and inadvertently delete all of your data. To prevent this from happening consider using the Execution guard feature in ApexSQL Complete, to warn against such potentially damaging actions, before you execute them. Learn more: Execution alerts

    注意:可能发生的不幸错误是意外地运行了不带Where子句SQL Delete并无意间删除了所有数据。 为防止这种情况发生,请在执行之前考虑使用ApexSQL Complete中的Execution保护功能,以警告此类可能有害的操作。 了解更多: 执行警报

    如何使用带有where子句的Top删除行 (How to delete rows using Top with where clause)

    The following example deletes 50 random rows from the Person.Person table in the AdventureWorks2014 database. The value in the BusinessEntityID must be in between 30,000 and 40,000

    下面的示例从AdventureWorks2014数据库的Person.Person表中删除50个随机行。 BusinessEntityID中的值必须介于30,000和40,000之间

    USE Adventureworks2014;
    GO
    DELETE TOP(50) FROM [Person].[Person]
    WHERE BusinessEntityID between 30000 and 40000
    

    Note: The when the TOP (n) clause is used with the SQL Delete statement and any DML statement (i.e. Select, Insert, Delete and Update), the operation is performed on a random selection of a number of rows specified in the Top clause.

    注意:当TOP(n)子句与SQL Delete语句和任何DML语句(即Select,Insert,Delete和Update)一起使用时,将对Top子句中指定的许多行的随机选择执行操作。

    如何删除重复的行 (How to delete duplicate rows)

    In the real-world, we tend to gather data from different sources; it’s not uncommon to have duplicate records. One approach to the duplicate problem is first to identify where the duplicates have occurred. And run a select query on those columns.

    在现实世界中,我们倾向于从不同的来源收集数据。 有重复的记录并不少见。 解决重复问题的一种方法是首先确定重复发生在哪里。 并对这些列运行选择查询。

    EATE TABLE tb_spaceused
    (database_name       NVARCHAR(128), 
     database_size       VARCHAR(18), 
     [unallocated space] VARCHAR(18), 
     reserved            VARCHAR(18), 
     data                VARCHAR(18), 
     index_size          VARCHAR(18), 
     unused              VARCHAR(18)
    );
    INSERT INTO tb_spaceused
    EXEC sp_msforeachdb 
         @command1 = "use ? exec sp_spaceused  @oneresultset = 1";
     
    SELECT *
    FROM tb_spaceused
    order by database_name
    

    The following example uses the PARTITION BY argument to partition the query result set by all the columns of tb_spaceused table. The Row_Number (), a window function, which means it operates over an ordered set. The ORDER BY clause specified in the OVER clause orders the rows in each partition by the entire columns tb_spaceused table.

    以下示例使用PARTITION BY参数将查询结果集按tb_spaceused表的所​​有列进行分区 。 Row_Number()是一个窗口函数,这意味着它将对有序集进行操作。 OVER子句中指定的ORDER BY子句按tb_spaceused表的整个列对每个分区中的行进行排序。

    WITH CTE
         AS (SELECT *, 
                    ROW_NUMBER() OVER(PARTITION BY database_name, 
                                                   database_size, 
                                                   [unallocated space], 
                                                   reserved, 
                                                   data, 
                                                   index_size, 
                                                   unused
                    ORDER BY database_name
                            ) AS Row_Num
             FROM tb_spaceused)
         SELECT *
         FROM CTE
         WHERE Row_Num <> 1;
    

    The following example uses the PARTITION BY argument to partition the query result set by all the columns of tb_spaceused table.

    Replacing the Select statement with a Delete removes all the duplicates of the table.

    用Delete替换Select语句将删除表的所有重复项。

    WITH CTE
         AS (SELECT *, 
                    ROW_NUMBER() OVER(PARTITION BY database_name, 
                                                   database_size, 
                                                   [unallocated space], 
                                                   reserved, 
                                                   data, 
                                                   index_size, 
                                                   unused
                    ORDER BY database_name
                            ) AS Row_Num
             FROM tb_spaceused)
         --SELECT *
         --FROM CTE
         --WHERE Row_Num <> 1;
    	 DELETE FROM CTE
         WHERE Row_Num <> 1;
    

    Replacing the Select statement with a Delete removes all the duplicates of the table.

    如何使用SQL子查询删除行 (How to delete rows using SQL sub-queries)

    In the following example, the rows in one table are deleted based on data in another table. In the examples, the rows from the SalesPersonQuotaHistory table are deleted based on the SalesYTD column of the SalesPerson table.

    在以下示例中,一个表中的行基于另一表中的数据被删除。 在示例中,根据SalesPerson表的SalesYTD列删除SalesPersonQuotaHistory表中的行。

    DELETE FROM Sales.SalesPersonQuotaHistory
    WHERE BusinessEntityID IN
    (
        SELECT BusinessEntityID
        FROM Sales.SalesPerson
        WHERE SalesYTD > 4900000.00
    ); 
    GO
    

    如何使用SQL联接删除行 (How to delete rows using SQL Joins )

    In this section, we will use the SQL Delete statement to delete the data from the Adeventureworks2014 database. Deleting data, at first sight, sound trivial, but once we get into a large database design things might not be same and easy anymore.

    在本节中,我们将使用SQL Delete语句从Adeventureworks2014数据库中删除数据。 乍一看,删除数据似乎微不足道,但是一旦我们进入大型数据库设计,事情可能就不再那么简单了。

    In many cases, the tables are related via a primary and foreign key relationship. In the following example, we can see a use of joins to delete the data from the Sales.SalesPersonQuotaHistory.

    在许多情况下,这些表通过主键和外键关系进行关联。 在以下示例中,我们可以看到使用联接从Sales.SalesPersonQuotaHistory中删除数据

    DELETE sq
    FROM Sales.SalesPersonQuotaHistory sq
         INNER JOIN Sales.SalesPerson sp ON sq.BusinessEntityID = sp.BusinessEntityID
    WHERE sp.SalesYTD > 4500000.00;  
    GO
    

    如何使用链接的服务器和OpenQuery从远程表中删除行 (How to delete rows from a remote table using linked servers and OpenQuery)

    The following example uses the SQL delete statement to delete rows from a remote table using the linked server named, hqdbt01. Then query the remote table using four-part object naming convention to delete the rows from the remote table

    下面的示例使用SQL delete语句使用名为hqdbt01的链接服务器从远程表中删除行。 然后使用四部分对象命名约定查询远程表以从远程表中删除行

    DELETE
    FROM [hqdbt01].AdventureWorks2014.[HumanResources].[Shift]
    WHERE ShiftID = 2;
    

    The following example, the remote table is queried by specifying the OPENQUERY rowset function along with the delete command.

    在以下示例中,通过指定OPENQUERY行集函数以及delete命令来查询远程表。

    DELETE OPENQUERY (hqdbt01, 'SELECT *
    FROM AdventureWorks2014.HumanResources.Department  
    WHERE DepartmentID = 18');
    

    如何使用SSMS删除行 (How to delete rows using SSMS)

    Using the SQL Server Management Studio (SSMS), Graphical User Interface (GUI) to delete rows involves a manual search. In reality, it will be much easier and quicker to delete records with a SQL query.

    使用SQL Server Management Studio(SSMS),图形用户界面(GUI)删除行涉及手动搜索。 实际上,使用SQL查询删除记录将更加容易和快捷。

    Let’s go ahead and locate the table to use a SQL delete statement, in this case, table dbo.cities is selected. Now, right-click and choose Edit Top 200 rows. This option opens up a query designer window. Next, right-click the window and select Execute SQL and write a new query that will delete rows from the dbo.cities table.

    让我们继续查找表以使用SQL delete语句,在这种情况下,将选择表dbo.cities 。 现在,右键单击并选择编辑前200行 。 此选项将打开查询设计器窗口。 接下来,右键单击该窗口并选择Execute SQL并编写一个新查询,该查询将从dbo.cities表中删除行。

    How to delete rows using SSMS

    In the result pane, make sure that SELECT Statement is pulling up the correct targeted records before start deleting rows. Select the rows and right-click the rows and choose Delete to remove the rows from the table.

    在结果窗格中,在开始删除行之前,请确保SELECT语句提取正确的目标记录。 选择行并右键单击行,然后选择“ 删除”以从表中删除行。

    SQL delete - Select the rows and right-click the rows and choose Delete to remove the rows from the table.

    摘要 (Summary)

    Thus far, we’ve seen many different ways use the SQL delete statement to remove data. But, there is a list of the consideration to be followed while using the delete statement, and it as follows:

    到目前为止,我们已经看到使用SQL delete语句删除数据的许多不同方式。 但是,在使用delete语句时,有一个注意事项列表,如下所示:

    1. It is always recommended to start with a SELECT statement before you delete anything to make sure that you’re targeting the correct records. So the delete statement is used to delete rows from a table using the where clause to select only the rows to be deleted

      始终建议从SELECT语句开始,然后再删除任何内容,以确保定位的是正确的记录。 因此,delete语句用于使用where子句从表中删除行,以仅选择要删除的行
    2. Always use a unique identifier to locate the rows that you need to delete

      始终使用唯一标识符查找需要删除的行
    3. To delete all the rows in a table, always use TRUNCATE TABLE. TRUNCATE TABLE which is faster than a SQL delete statement and it uses fewer system and transaction-log resources

      要删除表中的所有行,请始终使用TRUNCATE TABLE。 TRUNCATE TABLE比SQL delete语句快,并且使用较少的系统和事务日志资源
    4. By default, DELETE statements induce an exclusive (X) lock on the table, and it holds the lock until the transaction completes

      默认情况下,DELETE语句在表上引入互斥(X)锁,并持有该锁,直到事务完成为止
    5. NOLOCK hint or read uncommitted NOLOCK提示或读取未提交的isolation level 隔离级别允许读取操作
    6. It is recommended to specify the TABLOCK hint in the delete statement. This process allows page de-allocation and associated space available for reuse by other objects in the database

      建议在delete语句中指定TABLOCK提示。 此过程允许页面解除分配以及相关的空间可用于数据库中的其他对象重用
    7. It is good practice to create a clustered index on the heap table before executing a delete statement

      优良作法是在执行删除语句之前在堆表上创建聚簇索引
    8. Although very simple and very powerful, and the result of a Delete statement is destructive. Deleted rows cannot be easily recovered

      尽管非常简单且非常强大,但Delete语句的结果却具有破坏性。 删除的行无法轻易恢复

    Note: To recover deleted rows see SQL Server disaster recovery – How to quickly recover data lost due to an Inadvertent delete operation

    注意:要恢复已删除的行,请参阅SQL Server灾难恢复–如何快速恢复由于无意删除操作而丢失的数据

    That’s all for now… Hope you enjoy reading this article on the SQL delete statement. If you have any questions, feel free to comment below.

    现在就这些了……希望您喜欢阅读有关SQL delete语句的本文。 如有任何疑问,请在下面发表评论。

    翻译自: https://www.sqlshack.com/overview-of-the-sql-delete-statement/

    sql delete语句

    展开全文
  • SQL DELETE 语句的用法

    万次阅读 2020-07-06 09:35:44
    DELETE 语句用于删除表中的行。 语法 DELETE FROM 表名称 WHERE 列名称 = 值 例表 LastName FirstName Address City Gates Bill Xuanwumen 10 Beijing Wilson Fred Zhongshan 23 ...

    DELETE 语句用于删除表中的行。

    语法

    DELETE FROM 表名称 WHERE 列名称 = 值

    例表

    LastNameFirstNameAddressCity
    GatesBillXuanwumen 10Beijing
    WilsonFredZhongshan 23Nanjing

    删除某行

    "Fred Wilson" 会被删除:

    DELETE FROM Person WHERE LastName = 'Wilson'

    结果:

    LastNameFirstNameAddressCity
    GatesBillXuanwumen 10Beijing

    删除所有行

    可以在不删除表的情况下删除所有的行。这意味着表的结构、属性和索引都是完整的:

    DELETE FROM table_name

    或者

    DELETE * FROM table_name

    delete 与 truncate 应用区别:

    1、对于删除整个表的所有数据时,delete并不会释放表所占用的空间

    2、如果用户确定是 删除 整表的所有数据,那么使用 truncate table 速度更快

    --刪除所有部門信息:使用delete
    delete from table_name;
    --刪除所有部門信息:TRUNCATE
    truncate table table_name;

    DELETE例子

    请参考具有以下记录的CUSTOMERS表:

    ID  NAME       AGE       ADDRESS            SALARY 
    1   Ramesh     32        Ahmedabad          2000.00 
    2   Khilan     25        Delhi              1500.00 
    3   kaushik    23        Kota               2000.00 
    4   Chaitali   25        Mumbai             6500.00 
    5   Hardik     27        Bhopal             8500.00 
    6   Komal      22        MP                 4500.00 
    7   Muffy      24        Indore             10000.00

    以下命令是一个示例,将删除ID为6的客户的记录:

    DELETE FROM CUSTOMERS WHERE ID = 6;

    删除后CUSTOMERS表的记录如下:

    ID  NAME       AGE       ADDRESS              SALARY 
    1   Ramesh     32        Ahmedabad            2000.00 
    2   Khilan     25        Delhi                1500.00 
    3   kaushik    23        Kota                 2000.00 
    4   Chaitali   25        Mumbai               6500.00 
    5   Hardik     27        Bhopal               8500.00 
    7   Muffy      24        Indore               10000.00

    如果你想删除CUSTOMERS表中的所有记录,则不需要使用WHERE子句。

    DELETE FROM CUSTOMERS;

    执行后,CUSTOMERS表将不会有任何记录。


    原文:SQL DELETE 语句的用法

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  • SQLDELETE 语句

    万次阅读 2018-05-09 09:39:36
    DELETE 语句DELETE 语句用于删除表中的行。语法DELETE FROM 表名称 WHERE 列名称 = 值Person:LastNameFirstNameAddressCityGatesBillXuanwumen 10BeijingWilsonFredZhongshan 23Nanjing删除某行"Fred ...
  • SQL Delete 语句(删除表中的记录)

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    SQL DELETE 语句  DELETE语句用于删除表中现有记录。 SQL DELETE 语法 DELETE FROM table_name WHERE condition; 请注意删除表格中的记录时要小心!注意SQL DELETE 语句中的 WHERE 子句! WHERE子句...
  • SQL入门之第九讲——DELETE删除语句

    千次阅读 2022-05-08 10:33:44
    定义:DELETE 语句是用于删除表中的一条或多条记录。 基本语法: DELETE FROM <表名> WHERE <筛选条件>; 1.DELETE删除语句 如果省略WHERE条件时,这回收DELETE 语句就会删除整个表的数据记录。 需要...
  • 文章目录SQL INSERT INTO 语句SQL UPDATE 语句SQL DELETE 语句 SQL INSERT INTO 语句 NSERT INTO 语句用于向表中插入新记录。 NSERT INTO 语句可以有两种编写形式。 第一种形式无需指定要插入数据的列名,只需提供被...
  • Oracle SQLdelete删除语句总结

    万次阅读 2015-03-27 16:40:40
    Oracle delete sql 语句总结:1、delete 用于删除表中的某行或整个数据表中的数据;2、 truncate也可用于删除整个表里面的数据,truncate释放空间,速度更快
  • SQL delete语句 之多表删除 总结

    万次阅读 2018-12-13 01:57:15
    delete语句用于删除表中已经存在的整行数据 Tbl_name关键词代表删除数据的目标表 Where子句代表被删除数据的满足条件,如果没有where子句则代 表所有表数据都删除 Order by子句代表删除数据的顺序 Limit子句...
  • MySQL delete 语句

    万次阅读 2022-04-13 15:48:34
    mysql 中delete语句主要分为三个层次,下面简单介绍下 1. 最基础的条件删除,如下所示 DELETE FROM table_name where table_name.name='dell' 还有一种按序删除的方式如下 DELETE FROM customers ORDER BY Name ...
  • SQL 删除语句怎么写呢?

    千次阅读 2021-01-19 23:29:16
    我的SQL语句是这样写的:deletefromstudentInfowherestuid=2...我的SQL语句是这样写的:delete from studentInfo where stuid = 2但是、所影响的行数为 0数据库中的记录并没有少!是哪里出了问题?另外一个问题!我...
  • MySQL DELETE 语句

    2020-12-16 17:06:06
    以下是 SQL DELETE 语句从 MySQL 数据表中删除数据的通用语法: DELETE FROM table_name [WHERE Clause] 如果没有指定 WHERE 子句,MySQL 表中的所有记录将被删除。 你可以在 WHERE 子句中指定任何条件 您可以在...
  • SQL怎么用DELETE删除多条数据

    千次阅读 2021-03-04 02:54:37
    展开全部1、首先创建一个临时表,用于演示sqlserver语法中delete删除的使用方法IF OBJECT_ID('tempdb..#tblDelete') IS NOT NULL DROP TABLE #tblDelete;CREATE TABLE #tblDelete(Code varchar(50),Total int);2、...
  • SQL中的DELETE语句

    千次阅读 2014-12-15 11:00:12
    要从表中删除一个或多个记录,需要使用SQL DELETE语句。你可以给DELETE 语句提供WHERE 子句。WHERE子句用来选择要删除的记录。 例如,下面的这个DELETE语句只删除字段first_column的值等于’Delete Me’的记录: ...
  • 批量删除sql语句

    千次阅读 2019-09-23 13:06:08
    SELECT CONCAT("DELETE FROM supplier_change_log WHERE old_supplier_id=4194 AND id>=",@I," AND id<",@I:=@I+2000,";SELECT SLEEP(0.2);") FROM supplier_change_log LIMIT 1205; 转载于:h...
  • DELETE 语句用于删除表中的行。语法如下DELETE FROM 表名称 WHERE 列名称 = 值例如:DELETE FROM user WHERE name = 'Wilson' 当表名使用别名时,语法如下DELETE 别名 FROM 表名称 别名 WHERE 列名称 = 值例如:...
  • 使用SQL语句DELETE删除表中数据

    千次阅读 2021-10-10 16:16:22
    使用SQL语句DELETE删除表中数据 基本语法格式如下: FROM:可选关键字,用在DELETE关键字与目标table_or_view_name。 <OUTPUT_Clause>:将已删除行或这些行表达式作为DELETE操作的一部分返回。 FROM <...
  • SQL语句Delete的级联操作

    千次阅读 2014-08-18 02:18:01
    设备状态表中有很多设备的状态 delete device_status a from device_status a inner join device_file b on a.device_id=b.colId and b.colGroupId='video'; select * from device_status;
  • 转载-增删改查sql语句语法

    千次阅读 2021-05-06 05:30:41
    一、增:有2种方法1.使用insert插入单行数据:语法:insert [into] [列名] values 例:insert into Strdents (姓名,性别,出生...使用insert,select语句将现有表中的 数据添加到已有的新表中语法:insert into select...
  • 主要介绍了SQL删除语句DROP、TRUNCATE、 DELETE 的区别,帮助大家更好的理解和学习sql语句,感兴趣的朋友可以了解下
  • delete 的用法(Hive)(SQL)

    千次阅读 2021-10-12 17:39:30
    此题需要注意的是题目要求是删除,故而不能...delete from Person where Id in ( select t1.Id from( select Id,Email, row_number()over(partition by Email order by Id) rn from Person ) t1 where t1..
  • Query query = session.createQuery("delete Student s where s.id=?"); query.setInteger(0, 1); query.executeUpdate(); tx.commit(); } catch (HibernateException e) { tx.rollback(); e.printStackTrace...
  • sql中有三种删除语句 delete、drop、truncate 1.delete 基础用法:delete from table(表名) [where] 用法理解:用于删除有明确定义的数据或者整个表的数据。比如:id是唯一不可重复的,delete from Studentwhere...
  • PostgreSQL DELETE 语句

    2020-12-16 17:27:13
    PostgreSQL DELETE 语句 你可以使用 DELETE 语句来删除 PostgreSQL 表中的数据。 语法 以下是 DELETE 语句删除数据的通用语法: DELETE FROM table_name WHERE [condition]; 如果没有指定 WHERE 子句,PostgreSQL 表...
  • 本文从SQL语句格式角度,谈一谈SQL更新语句的基本格式及其在Oracle中的实践经验(使用场景、注意事项)。可供数据库管理系统学习者、数据分析员、数据统计员、不太熟悉SQL的程序员等参考。
  • 关联两表删除两表内容 delete t1,t2  from t_pic as t1 left join t_pic_muc_comments as t2 on t1.pmcid=t2.pmcid  where t1.pid=1
  • SQl语句的级联删除问题删除应该有顺序1,删除link表delete from ref,link where ref.link_code=link.link_code and link_id=?delete from link where link_id=?2,删除plan表delete from ref,plan where ref.plan_...
  • spark sql如何执行delete

    2018-12-10 13:02:52
    请问大家,spark sql如何执行delete和update操作呢?(hive除外)。单纯说的,只用spark sql能否实现呢?谢谢
  • SQL语句中EXISTS的用法

    千次阅读 2021-07-24 16:33:59
    记录:258 在业务开展中,会遇到类似需求...在SQL语句中EXISTS的用法,能够比较简洁的去解决这类需求。 一、建表 1.在MySQL数据库建表语句 CREATE TABLE TEST_TB01 ( sensor_id BIGINT, part_id BIGINT, f

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