MySQL之where查詢
阿新 • • 發佈:2019-02-10
比較運算
只顯示id,name: select id,name from students;
消除重複行distinct
select distinct gender from students;
條件
select * from students where id>3;
select * from students where isDelete=0;
邏輯運算
- and
- or
- not
select * from students where id>3 and gender=0;
select * from students where id<4 or isDelete=0 ;
模糊查詢
- like
- % : 表示任意多個字元
- _ : 表示一個任意字元
查詢姓羅的人:
select * from students where name like '羅%';
查詢姓楊 且 名字是一個字的人:
select * from students where name like '楊_';
查詢姓薛 且 名字兩個字的人:
select * from students where name like '薛__';
查詢姓羅 或者 叫嫣 的人:
select * from students where name like '羅%' or name like '%嫣';
範圍查詢
- in :表示在一個非連續的範圍內
- 查詢編號是1或3或8的人
select * from students where id in(1,3,8);
- between ... and ... 表示在一個連續的範圍內(between後小數,and後大數)
- 查詢id是3到8的人
select * from students where id between 3 and 8;
select * from students whereid between 3 and 8andgender=1;
空判斷
- null與''不相同
- 判斷: is null
select * from students where birthday is null;
select * from students where birthday is not null;
優先順序
- 小括號, not, 比較運算子, 邏輯運算子
- and比or先運算,如果同時出現並希望先算or,需要結合()使用