使用:select 内容 from 表名 inner join 表名 on 连接条件 where 普通筛选条件 select * from emp inner join dept on emp.deptno=dept.deptno where sal>2000-- 显示内连接 2)外连接: 左外连接:select 内容 from 表名 left outer join 表名 on 连接条件 查询员工姓名,工作,薪资,部门名称及没有部门的员...
a JOIN allows you to retrieve data from two tables. This section will briefly discuss how several PostgreSQL JOIN types, including CROSS JOIN, INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL OUTER JOIN.
FROM employees e LEFT OUTER JOIN departments d ON e.department_id=d.department_id; #右外连接 SELECT last_name,department_name FROM employees e RIGHT OUTER JOIN departments d ON e.department_id =d.department_id; #满外连接: mysql不支持full outer join的方式 SELECT last_name,department_name FR...
PostgreSQL中,计划节点分为四类,分别是控制节点(Control Node)、扫描节点(Scan Node)、物化节点(Materializtion Node)、连接节点(Join Node) 1.控制节点:处理特殊情况的节点,用于实现特殊的执行流程,如Result节点可用来表示INSERT语句中VALUES子句指定的将要插入的元组 2.扫描节点:用于扫描表等对象以从中获取元组。SeqS...
The PostgreSQL LEFT JOIN, joins two tables and fetches rows based on a condition, which are matching in both the tables, and the unmatched rows will also be available from the table written before the JOIN clause.
Left Join– select rows from one table that may or may not have the corresponding rows in other tables. Self-join– join a table to itself by comparing a table to itself. Full Outer Join– use the full join to find a row in a table that does not have a matching row in another tab...
Hive的Join的文档说明地址： https://cwiki.apache.org/confluence/display/Hive/LanguageManual%2BJoins ...
上一章节已介绍了如何识别分区表并找到所有的分区子表以及函数expand_inherited_tables的主要实现逻辑,该函数把子表信息放在root(PlannerInfo)->append_rel_list链表中。为了更好的理解相关的逻辑,本节重点介绍分区表查询相关的重要数据结构,包括RelOptInfo/PlannerInfo/AppendRelInfo.一...
fetchedFROMpg_tables tLEFT OUTER JOINpg_class cONt.tablename=c.relnameLEFT OUTER JOIN(SELECTc.relnameASctablename,ipg.relnameASindexname,x.indnattsASnumber_of_columns, idx_scan, idx_tup_read, idx_tup_fetch, indexrelname, indisuniqueFROMpg_index xJOINpg_class cONc.oid=x.indrelidJOINpg_class...
SYSINDEXES IND LEFT OUTER JOIN SYSIBM.SYSKEYS COL ON IND.CREATOR = COL.IXCREATOR AND IND.NAME = COL.IXNAME INNER JOIN SYSIBM.SYSTABLES T ON IND.CREATOR=T.CREATOR AND IND.TBNAME=T.NAME WHERE IND.CREATOR NOT LIKE 'SYS%' AND IND.UNIQUERULE ...