普通条件查询

• 语法：SELECT col_list FROM table_name WHERE condintion_expression
• 例子：SELECT *FROM games WHERE GNO=9
• 例子：SELECT *FROM games WHERE score>2500
• 例子：SELECT *FROM users WHERE user_qq=1 AND score>400
• 特点：查询符合WHERE关键字后面的条件
• 逻辑运算符：AND，OR，NOT(非)

模糊查询

• 语法：SELECT *FROM table_name WHERE col_name BETWEEN number1 AND number2
• 特点：利用BETWEEN, AND关键字查询number1（包括）到number2（包括）范围的数据
• 例子：SELECT *FROM games WHERE GNO BETWEEN 2 AND 8
• 语法：SELECT *FROM table_name WHERE col_name NOT BETWEEN number1 AND number2
• 特点：查询不在number1到number2范围内的数据
• 例子：SELECT *FROM games WHERE GNO NOT BETWEEN 2 AND 9
• 通配符
  

例子：SELECT *FROM users WHERE user_name LIKE ‘孙%’
例子：SELECT *FROM users WHERE user_name NOT LIKE ‘孙%’

查询空值的运算符
语法：SELECT *FROM table_name WHERE col_name IS（NOT） NULL