if exists(SELECT 1 FROM table WHERE id=@id) begin // do something here... end Any help would be greatly appreciated! On another note, I read that there are plans, or at least a feature request, to support something along the lines of T-SQL's @@ERROR, where in you can ch...
if exists 判断括号里的select语句是否有返回的行，也就是是否有结果集，如果有则执行判断为真的sql，与之相对是if not exists，如果没有返回行，则执行判断为真的sql这句话的意思我用程序中的if 跟你介绍if exists(SQL查询) 相当于 if(条件)下面我就不解释了
第一种:select的结果列数m小于原数据表的列数n,那么将select的结果插入到数据表的最有表,左边n-m列以默认值填充。 第二种:m>n,报错。 官方英文描述如下: For CREATE TABLE … SELECT, if IF NOT EXISTS is given and the table already exists, MySQL handles the statement as follows: The table defini...
问PHP SQL -基于if exists的SELECT内的OR条件EN相关子查询执行过程：先在外层查询中取“学生表”的第...
For example, we have decided we wish to replace our id = 1 record of Green Eggs and Ham and revert it back to the original In Search of Lost Time record instead. We can therefore take our original INSERT statement and add the new ON DUPLICATE KEY UPDATE clause: mysql> SET @id = 1...
Where name=’my_trig’and type=’tr’) (整个If语句 1分) Drop trigger my_trig (0.5分) Go (0.5分) Create trigger my_trig (1分) On student (0.5分) For Delete (1分) As (0.5分) Delete From sc (2分) Where 学号 in (Select 学号 From Deleted) (1分+2分) ...
if exists(select * from sysobjects where [name]='scoreTable') drop table scoreTable go create table scoreTable ( stuName char(10), courseName char(10), score int ) go insert scoreTable values('张三','语文',80) insert scoreTable values('张三','数学',86) ...
if exists (select * from dbo.sysobjects where id = object_id(N’[dbo].[函数名]’) and xtype in (N’FN’, N’IF’, N’TF’)) drop function [dbo].[函数名] 7 获取用户创建的对象信息 Sql代码 SELECT [name],[id],crdate FROM sysobjects where xtype=’U’ ...
if exists (select * from dbo.sysobjects where id = object_id(N’[dbo].[函数名]’) and xtype in (N’FN’, N’IF’, N’TF’)) drop function [dbo].[函数名] 7 获取用户创建的对象信息 Sql代码 SELECT [name],[id],crdate FROM sysobjects where xtype=’U’ ...
> records and then to perform an IF statement. I > agree with Naveen that this is an inefficient method. How much inefficient? Speed-inefficient? I don't think so... Code-inefficient? How about: IF (SELECT COUNT(*) FROM FROM table Where ID = PARAMID) THEN... Test case: ...