參考：https://www.imooc.com/learn/1281
語法格式:
SELECT 字段名 FROM 表名 WHERE 條件;
1.比較運算符
> 大于饿悬、< 小于克胳、<= 小于等于寺渗、>= 大于等于、= 等于件舵、<>不等于、!= 不等于
SELECT * FROM student WHERE mark >= 90;
SELECT * FROM student WHERE mark <= 85;
SELECT * FROM student WHERE sname = 'Jack';
SELECT * FROM student WHERE mark <> 86;
SELECT * FROM student WHERE sname != 'Bob';
Snipaste_2020-10-10_11-06-37.png
2.邏輯運算符
and 多個條件同時滿足
or 多個條件其中一個滿足
not 不滿足
SELECT * FROM student WHERE mark >= 85 AND mark <= 95;
SELECT * FROM student WHERE mark <= 85 OR id >= 3;
SELECT * FROM student WHERE NOT mark <> 86;
Snipaste_2020-10-10_13-25-48.png
3.int關(guān)鍵字
SELECT 字段名 FROM 表名 WHERE 字段 in (數(shù)據(jù)1, 數(shù)據(jù)2...);
in里面的每個數(shù)據(jù)都會作為一次條件娶靡，只要滿足條件的就會顯示漱凝，括號里可以是SQL語句
SELECT * FROM student WHERE id in(1,3,5);
SELECT * FROM student WHERE id NOT in(1,3,5);
Snipaste_2020-10-10_13-29-03.png
4.范圍查詢
SELECT 字段名 FROM 表名 WHERE 字段 BETWEEN 值1 AND 值2;
包含值1和值2，值2>=值1惰瓜，否則查不到
SELECT * FROM student WHERE mark BETWEEN 85 AND 95;
SELECT * FROM student WHERE mark BETWEEN 95 AND 85;
Snipaste_2020-10-10_13-51-52.png
5.模糊查詢like
SELECT * FROM 表名 WHERE 字段名 LIKE '通配符字符串';
%: 表示0個或多個字符(任意個字符)
_: 表示一個字符
注意：不區(qū)分大小寫
SELECT * FROM student WHERE sname LIKE 'R%';
SELECT * FROM student WHERE sname LIKE '%y';
SELECT * FROM student WHERE sname LIKE '%r%';
SELECT * FROM student WHERE sname LIKE 'R___'; --三個_
Snipaste_2020-10-10_14-12-06.png
