UPDATE tb_bookcase SET name= (SELECT bookname FROM tb_bookinfo WHERE tb_bookinfo.type =tb_bookcase.type AND tb_bookinfo.ord_date IN (SELECT MAX(ord_date) FROM tb_bookinfo)) WHERE tb_bookcase.subject='理学'; 第二种: 语法: UPDATE table1 inner/left/right join table2/(selectcolumnsfromtabl...
1、创建两个测试表，create table test_up_a(id number, value varchar2(100));create table test_up_b(id number, value varchar2(100));2、分别往两个表中插入数据；insert into test_up_a values(1,'A1');insert into test_up_a values(2,'A2');insert into test_up_a values(3,...
在一次准备处理历史数据sql时,出现这么一个问题:You can't specify target table '表名' for update in FROM clause,大致的意思就是:不能在同一张表中先select再update。 在此进行一下复盘沉淀,使用测试sql复现当时的场景(mysql是8版本),准备测试数据: CREATE TABLE `student` ( `id` int NOT NULL, `name`...
AI代码解释 SELECT*FROMfoodsWHEREid=1FORUPDATE;SELECT*FROMfoodsWHEREid=1and name=‘码农编程进阶笔记’FORUPDATE; 例2: (明确指定主键/索引,若查无此记录,无锁) 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECT*FROMfoodsWHEREid=-1FORUPDATE; 例3: (无主键/索引,表级锁) 代码语言:javascript ...
INNER JOIN Table1 ON (Table2.ColA = Table1.ColA); 实际更新的操作是在要更新的表上进行的,而不是在from子句所形成的新的结果集上进行的。 Oracle没有update from语法,可以通过两种写法实现同样的功能: 1:子查询UPDATE A SET A.NAME=(SELECT B.NAME FROM B WHERE B.ID=A.ID),本查询要根据具体情况看...
update a set value = 'test' from a join b on a.b_id = b.id join c on b.c_id = c.id where a.key = 'test' and c.value = 'test'; 按照上边的sql,本意是a、b、c三表关联,当c的value是’test’且a的key也是’test’的时候,就将a的value也改为’test’。但实际上这个sql有大问题,...
SQL Update From Select The problem with the simple UPDATE statement is that it can only take a single table. Why would we want to include a second table? We may have acolumn in one tablebut thevalues for that are derived or calculated from data in another table. ...
SQL Server supports the standard SQL to update the data in the table. Use the UPDATE TABLE statement to update records in the table in SQL Server. Syntax: UPDATE table_name SET column_name1 = new_value, column_name2 = new_value, ... [WHERE Condition]; ...
SQL UPDATE one column example Suppose Janet, who has employee id 3, gets married so that you need to change her last name in theemployeestable. The record of Janet in the employees before updating is as follows: SELECTemployeeid, lastname, firstnameFROMnorthwind_bk.employeesWHEREemployeeid =...
DELETE FROM 表名 [WHERE 条件]; TRUNCATE 表名;TRUNCATE是DDL语句,它只能删除表中的所有数据,不能根据条件删除,也不能删除表结构; DROP TABLE 表名;直接删除表; 如果表中含有外键约束,DDL语句不能直接删除表,只能先删除外键约束才能删除表。 DQL 数据查询语言(Data QueryLanguage,DQL)用于查询数据,以SELECT为核...