SQL UNION 和 UNION ALL 操作符

最新推荐文章于 2025-01-16 08:30:00 发布

转载最新推荐文章于 2025-01-16 08:30:00 发布 · 63 阅读

0 ·

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/lqsilly/archive/2013/03/29/2989552.html

本文详细解释了SQL UNION操作符的功能，包括其语法、如何避免重复值以及如何使用UNIONALL。通过一个具体示例展示了如何在查询中使用UNION，包括筛选条件和分组操作。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

　　UNION 操作符用于合并两个或多个 SELECT 语句的结果集。请注意，UNION 内部的 SELECT 语句必须拥有相同数量的列。列也必须拥有相似的数据类型。同时，每条 SELECT 语句中的列的顺序必须相同。SQL UNION 语法，SELECT column_name(s) FROM table_name1

　　UNION

SELECT column_name(s) FROM table_name2

注释：默认地，UNION 操作符选取不同的值。如果允许重复的值，请使用 UNION ALL。

　　SQL UNION ALL 语法

SELECT column_name(s) FROM table_name1 UNION ALL SELECT column_name(s) FROM table_name2另外，UNION 结果集中的列名总是等于 UNION 中第一个 SELECT 语句中的列名。
下面演示一个UNION实例和实例操作后显示数据

select max(dr.ScriptName) as 分类汇总,
sum(dr.ExecuteTrimLenght) as 业务函数总用时,
sum(dr.ExecuteTrimLenght) as 业务函数成功总用时,
0 as 业务函数失败总用时,

dr.IsSucceed as 成功与否
                                        from ScriptExecuteDetailResult as dr left join  ScriptExecuteResut as er on (dr.ser_id = er.id) left join
                                        TaskExecuteResult as ter on (er.ter_id = ter.id) left join 
                                        TaskOrders as eor on (ter.taskOrders_id = eor.id) left join ExecuteResult as er on (dr.ID = er.CaseId)
                                        where dr.isDel = 0  and dr.IsSucceed <> 'ON' 
                                        group by dr.ScriptName

union 
select max(dr.ScriptName) as 分类汇总,
sum(dr.ExecuteTrimLenght) as 业务函数总用时,
sum(dr.ExecuteTrimLenght) as 业务函数成功总用时,
0 as 业务函数失败总用时,

dr.IsSucceed as 成功与否
                                        from ScriptExecuteDetailResult as dr left join  ScriptExecuteResut as er on (dr.ser_id = er.id) left join
                                        TaskExecuteResult as ter on (er.ter_id = ter.id) left join 
                                        TaskOrders as eor on (ter.taskOrders_id = eor.id) left join ExecuteResult as er on (dr.ID = er.CaseId)
                                        where dr.isDel = 0  and dr.IsSucceed <> 'ON' 
and IsSucceed = '成功'
                                        group by dr.ScriptName

union 
select max(dr.ScriptName) as 分类汇总,
sum(dr.ExecuteTrimLenght) as 业务函数总用时,
0 as 业务函数总用时成功,
sum(dr.ExecuteTrimLenght) as 业务函数失败总用时,

dr.IsSucceed  as 成功与否
                                        from ScriptExecuteDetailResult as dr left join  ScriptExecuteResut as er on (dr.ser_id = er.id) left join
                                        TaskExecuteResult as ter on (er.ter_id = ter.id) left join 
                                        TaskOrders as eor on (ter.taskOrders_id = eor.id) left join ExecuteResult as er on (dr.ID = er.CaseId)
                                        where dr.isDel = 0  and dr.IsSucceed <> 'ON' 
and IsSucceed = '失败'
                                        group by dr.ScriptName

转载于:https://www.cnblogs.com/lqsilly/archive/2013/03/29/2989552.html