SELECTemployees.employee_id,employees.employee_name,departments.department_nameFROMemployeesFULLOUTERJOINdepartmentsONemployees.department_id=departments.department_id; 子查询(SUBQUERY):在查询中嵌入另一个查询以获得更灵活的数据结构。
FULL OUTER JOIN的韦恩图如下所示: 2左外连接:LEFT JOIN 左外连接又叫左连接 :意思是包含左边表所有记录,右边所有的匹配的记录,如果没有则用空补齐。换句话说就是,列出左边表全部的,及右边表符合条件的,不符合条件的以空值代替。 SQL>SELECTM.NAME, N.NAME, M.SEX, N.GRADE 2FROMMLEFTOUTERJOINNONM.NAME...
select c.customer_id,c.first_name,c.last_name from customers c left outer join(products p inner join purchases pr on p.product_id =pr.product_id and p.name='Supernova') on c.customer_id =pr.customer_id and p.product_id is null; 3.3完全外连接 1)定义 是左连接和右连接两者的结合 2...
FULL OUTER JOIN的韦恩图如下所示: 2左外连接:LEFT JOIN 左外连接又叫左连接 :意思是包含左边表所有记录,右边所有的匹配的记录,如果没有则用空补齐。换句话说就是,列出左边表全部的,及右边表符合条件的,不符合条件的以空值代替。 SQL>SELECTM.NAME, N.NAME, M.SEX, N.GRADE 2FROMMLEFTOUTERJOINNONM.NAME...
0.准备数据1.内连接:INNERJOIN2.左连接:LEFTJOIN3.右连接:RIGHTJOIN4.USING子句扩展知识点: 0.表别名的使用:1.group by的用法2.子查询1)不相关子查询2)相关子查询JOIN的含义就如英文单词“join”一样,连接两张表,语法如下所示:SELECT * FROM A INNER|LEFT|RIGHTJOIN& ...
2 FROM M LEFT OUTER JOIN N ON =; 1. 1. NAME NAME SEX GRADE 1. --- --- --- --- 1. kerry kerry male 3 1. jimmy jimmy male 2 1. tina female 1. wendy female 1. 1. SQL> SELECT , , M.SEX, N.GRADE 1. 2 FROM M LEFT JOIN N ON =; 1. ...
在使用子查询时，需要注意以下几点：1、通过查询快速创建表 create table test1(id,job,mgr,sal) as ...
select * from [表名1] left outer join [表名2] on 表名1.字段=表名2.字段 select * from [表名1],[表名2] where 表名1.字段=表名2.字段(+) 右连接 select * from [表名1] right outer join [表名2] on 表名1.字段=表名2.字段 ...
SQL> SELECT M.NAME, N.NAME, M.SEX, N.GRADE 2 FROM M LEFT OUTER JOIN N ON M.NAME=N.NAME; NAME NAME SEX GRADE --- --- --- --- kerry kerry male 3 jimmy jimmy male 2 tina female wendy female SQL> SELECT M.NAME, N.NAME, M.SEX, N.GRADE 2 FROM M LEFT JOIN N ON...
An outer join is such a join which is similar to the equi join, but Oracle will also return non matched rows from the table. Left Outer Join Thisleft outer joindisplays all matching records of both table along with the records in left hand side table of join clause which are not in ri...