昨天写 SQL Server 数据库上写 SQL 语句时,我原本想通过执行A left join B on ... and ...的操作,将查询结果中的两条记录合并成一条,奈何发现结果中依然有两条记录。 回顾了一下语法知识,意识到join on ... and ...的语句并不会对结果集的记录条数进行过滤。它的主要作用是,根据and后面指定的条件来...
--1.from --2.on --3.outer(join) --4.where --5.group by --6.cube|rollup --7.having --8.select --9.distinct --10.order by --11.top 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 1. 逻辑查询处理步骤序号 (8)SELECT (9)DISTINCT (11)<TOP_specification> (1)FROM <left_t...
通常情况下,多条件在 ON 子句中的执行顺序是由左至右,但这种顺序并不影响查询结果的正确性。然而,理解执行顺序有助于避免混淆和潜在的错误。 当使用多条件进行 JOIN 时,应遵循以下步骤: 1.明确指定连接类型:首先,确定要执行的连接类型(如 INNER JOIN、LEFT JOIN 等)。 2.单条件指定:其次,在 ON 子句中为...
SELECT * FROM a left join b on a.no=b.no WHERE b.title='标题3'
表1 left join 表2 on 表1.列 = 表2.列 表1 left join 表2 on 表1.列 = 表2.列 1. 例子 员工表关联部门表进行左外连接查询 思路: select * from 员工表 left join 部门表 on 员工表.外键列 = 部门表.主键列 代码: select * from employee left join department on employee.department_id =...
sqlserver inner join on 条件sqlserver inner join on条件 SQLServer中的INNER JOIN是根据指定的条件连接两个或多个表中的记录。INNER JOIN使用ON关键字指定连接条件。 例如,假设我们有两个表:表A和表B,我们想要连接这两个表,基于一个共同的条件,如列A的值等于列B的值,我们可以使用以下语法:...
LEFT join #B on #A.Lookup=#B.Lookup and #A.Val = 'B' and #B.Val in ('E') WHERE #B.Lookup is null Syntax-wise they look very similar but the results are very different and only the 1st one is correct. The explain plan is also very different. I researched this and it seems...
sys.tables a left join sys.extended_properties g on (a.object_id = g.major_id AND g.minor_id = 0) No 表名 说明 1 test_table 测试表 2 test_main - sqlserver的系统表 1、查看表和试图 SELECT * FROM sys.objects WHERE object_id = object_id('表名或视图名') ...
SQLServer使⽤LEFTJOINONLIKE进⾏数据关联查询 这是来新公司写的第⼀篇⽂章，使⽤LEFT JOIN ON LIKE处理⼀下这种问题：SQL视图代码如下：CREATE View[dbo].[VI_SearchCN]AS --搜索产品的⽂件 (select upload.FileId as ID,upload.Name as Title,upload.Name as FileTxt,con.TypeId as TypeId,...
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