SQL语句学习笔记☞select(待完善...)
2018-01-22 18:36
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1.查询整个表中所有语句:select *from tablename
2.查询某一列或几列: select column1,column2... from tablename
3.去重:SELECT DISTINCT column_name,column_name
FROM table_name;
4.排序order by : (默认升序)
SELECT column_name,column_name
FROM table_name
ORDER BY column_name,column_name ASC|DESC;
5.limit,限制查询显示的数量
select column1... from tablename limit number
6.LIKE &通配符 (通配符与LIKE通常一块使用)
LIKE : select
column1,column2... from tablename
where colonum like pattern
通配符:
7.IN in允许在where中存在多个选项
select column1,column2... from tablename where colonumin (name1,name2...)
8.between...and...,用于选择两个数之间的值(闭区间)
select column1,column2... from tablename where colonumbetween value1and
value2;
9.多表查询之连接
内连接(INNER JOIN或JOIN):
select a.column1..., b.column1... from tablename1 a join tablename2 b on a.column=b.column
左连接(left join):select a.column1..., b.column1... from tablename1 a left join tablename2 b on a.column=b.column
右连接(right join):select a.column1..., b.column1... from tablename1 a right join tablename2 b on a.column=b.column
2.查询某一列或几列: select column1,column2... from tablename
3.去重:SELECT DISTINCT column_name,column_name
FROM table_name;
4.排序order by : (默认升序)
SELECT column_name,column_name
FROM table_name
ORDER BY column_name,column_name ASC|DESC;
5.limit,限制查询显示的数量
select column1... from tablename limit number
6.LIKE &通配符 (通配符与LIKE通常一块使用)
LIKE : select
column1,column2... from tablename
where colonum like pattern
通配符:
7.IN in允许在where中存在多个选项
select column1,column2... from tablename where colonumin (name1,name2...)
8.between...and...,用于选择两个数之间的值(闭区间)
select column1,column2... from tablename where colonumbetween value1and
value2;
9.多表查询之连接
内连接(INNER JOIN或JOIN):
select a.column1..., b.column1... from tablename1 a join tablename2 b on a.column=b.column
左连接(left join):select a.column1..., b.column1... from tablename1 a left join tablename2 b on a.column=b.column
右连接(right join):select a.column1..., b.column1... from tablename1 a right join tablename2 b on a.column=b.column
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