(SELECT deptno AVG(sal) as avg FROM t_emp GROUP BY deptno) t ON e.deptno=t.deptno AND e.sal >= t.avg; 1. 2. 3. 4. 5. 外连接 LEFT JOIN 外连接与内连接的区别在于,除了符合条件的记录之外,结果集中还会保留不符合条件的记录。 AI检测代码解析 // 例子 SELECT e.empno,e.ename ,d.dnam...
left join juren_card_sales as s on s.card_num=c.card_num where s.card_num='xq1t005t202616bj' 1. 2. 3. 比较:当 juren_card_sales 表没有建立索引 index_cs 的时候,耗时:0.0173m 建立后:耗时 0.0010m 提高 17倍 结论:暂时 看不出来 联表查询2: 代码示例: select c.*,s.* from `juren...
g.id as sort from cnto_fk a left join cnto b on a.pid=b.id left join project_table d on b.proj=d.pc_code left join sys_common g on a.fzno=g.cno and g.ctype='cnto_htlx' where 1=1 and d.project
在SQL中,我们可以使用LEFT JOIN关键字来实现这种操作。...右连接(RIGHT JOIN):右连接就像是将右表中的所有来宾都安排上座位,无论左表中是否有对应的来宾。在SQL中,我们可以使用RIGHT JOIN关键字来实现这种操作。...外连接(OUTER JOIN):外连接就像是将左表和右表中的所有来宾都安排上座位,无论他们是否有对应...
t JOIN sys.[schemas] s ON t.[schema_id] = s.[schema_id] JOIN sys.[columns] c ON t.[object_id] = c.[object_id] LEFT JOIN sys.[stats_columns] l ON l.[object_id] = c.[object_id] AND l.[column_id] = c.[column_id] AND l.[stats_column_id] = 1 LEFT JOIN sys.[exte...
t JOIN sys.[schemas] s ON t.[schema_id] = s.[schema_id] JOIN sys.[columns] c ON t.[object_id] = c.[object_id] LEFT JOIN sys.[stats_columns] l ON l.[object_id] = c.[object_id] AND l.[column_id] = c.[column_id] AND l.[stats_column_id] = 1 LEFT JOIN sys.[exte...
selectsnofromscwherecno<>'01';--错误, 这把学过01又学过02的人也算进去了selectdistinctsnofromscexcept(selectsnofromscwherecno='01'); -- 正解! 表的数据更新 insert into, update, delete from; 1.插入数据insert into 表名(属性) values (数据) ...
[PartitionScheme]FROMsys.tables AS tblINNER JOIN sys.indexes AS i ON (i.index_id > @_msparam_0 and i.is_hypothetical = @_msparam_1) AND (i.object_id=tbl.object_id)LEFT OUTER JOIN sys.data_spaces AS dsi ON dsi.data_space_id = i.data_space_idLEFT OUTER JOIN sys.stats AS s ...
[PartitionScheme]FROMsys.tables AS tblINNER JOIN sys.indexes AS i ON (i.index_id > @_msparam_0 and i.is_hypothetical = @_msparam_1) AND (i.object_id=tbl.object_id)LEFT OUTER JOIN sys.data_spaces AS dsi ON dsi.data_space_id = i.data_space_idLEFT OUTER JOIN sys.stats AS s ...
[object_id])ENDASassociated_entity,wt.blocking_session_id,wt.resource_descriptionFROMsys.dm_tran_locksASloLEFTJOINsys.partitionsASpONlo.resource_associated_entity_id=p.partition_idLEFTJOINsys.dm_os_waiting_tasksASwtONlo.lock_owner_address=wt.resource_addressWHERElo.request_session_id>50ANDlo....