1、 WHERE子句用法;
SELECT *
FROM stu_info
WHERE depart='中文系'
2、 根据条件查询数值数据;
SELECT *
FROM course
WHERE credit=4
SELECT cname,cno,credit
FROM course
WHERE creciit>2
SELECT sname,DATEDIFF(year,birthr GETDATE()) AS 年龄
FROM stu_info
WHERE DATEDIFF(year,birth,GETDATE())>30
3、 根据条件查询字符数据;
SELECT *
FROM stu_info
WHERE sname='张三'
SELECT *
FROM stu_info
WHERE depart<>'计算机系'
4、 根据条件查询日期数据;
SELECT *
FROM stu_info
WHERE birth>'01/20/1977'
5、 按范围查询数据;
SELECT *
FROM course
WHERE credit BETWEEN 2 AND 4
6、 查询NULL值;
SELECT *
FROM str_info
WHERE telephone is NULL