005.PGSQL-in、not in、exists、not exists、 using 的select查询、delete删除重复数据 使用及其效率对比 1. select 查询 in、not in、exists、not exists 的区别 exists 效率远远大于 in CREATESEQUENCE "ioc_dw_second"."test0002_seq" INCREMENT1MINVALUE1MAXVALUE9223372036854775807START1CACHE1CYCLE ;CREATETABLE...
查询语句:select tbl1.col1, tbl2.col2 from tbl1 inner join tbl2 using(col3) where tbl1.col1 in (5, 6); 假设MySQL按照查询中的表顺序进行关联操作,我们则可以用下面的伪代码表示MySQL将如何完成这个查询: outer_iter = iterator over tbl1 where col1 in (5, 6)outer_row = outer_iter.nextw...
This is the complete query I am using below. Hbm_Matter will only 1 have unique record(matter_uno). How do I get multiple records returned in my query when there are 2 records in the subquery? select matter_uno, matter_name, bill_empl_uno from hbm_matter a where exists ( select top...
Using where;Using index表示查询的列被索引覆盖,且where筛选条件是索引列前导列的一个范围,或者是索引列的非前导列,例如:select id from test where id > 5;。很明显,效率也很高。 Using where表示查询的列未被索引覆盖,且where筛选条件是索引列前导列的一个范围,或者是索引列的非前导列,或者是非索引列,例...
上面的sql中 订单表中(orders) 存在user_id,而又有用户表(users),所以我们用orders表中user_id和user表中的id 来in 和 exists。 结果 1.where后面是小表 (1)select count(1) from orders o where o.user_id in(select u.id from users u); ...
MySQL中连接SQL语句中,ON子句的语法格式为:table1.column_name = table2.column_name。当模式设计对联接表的列采用了相同的命名样式时,就可以使用USING语法来简化 ON 语法,格式为:USING(column_name)。 所以,USING的功能相当于ON,区别在于USING指定一个属性名用于连接两个表,而ON指定一个条件。另外,SELECT *时,...
完整SQL隐藏关键信息 explain select xx from a left join r on a.x= r.x where xx xx xx xx xx order by a.submitTime desc limit 0 , 10 查询a表进行一次回表操作 1强制使用索引 FORCE INDEX (ind_zzz) 没有任何效果 order by 字段建立索引 ...
1.2.14 SQL Functions Oracle Database Lite does not support trigonometric functions, SOUNDEX, or bit operations. 1.2.15 Locking and Transactions Oracle Database Lite begins a transaction with the first use of SELECT. In some isolation levels, the use of a SELECT on one connection can lock...
If you create a publication in the New Publication Wizard, the publication compatibility level is determined based on the options that you select on the Subscriber Types page of the wizard. In versions of SQL Server earlier than SQL Server 2005, the publication compatibility level automatically ...
Open SQL Server Management Studio. In the View menu, select Template Browser (Ctrl+Alt+T): You can see recently used templates at the bottom of the template browser. Expand the node you're interested in. Right-click the template, and then select Open: You can also double-click the templa...