4个基本操作
1.增INSERT
INSERT INTO 表 (字段列表) VALUES (值列表)
2.删DELETE
DELETE FROM 表 WHERE 条件
3.改
UPDATE 表 SET 字段=值,字段=值 WHERE 条件
4.查
SELECT * FROM WHERE 条件
子句
WHERE 条件
WHERE name='blue'
WHERE age>18
WHERE age<=18
WHERE age>=18 AND score<60
WHERE cach>100 OR score>10000
ORDER 排序
ORDER BY age ASC/DESC
ASC-升序(从小到大)
DESC-降序(从大到小)
ORDER BY price ASC
*价格(price)升序排序，如果价格相同，再按销量(sales)降序排序
ORDER BY price ASC, sales DESC
GROUP 聚类-合并相同
*统计每个班人数
ID class name
"1" "1" "小明"
"2" "2" "小红"
"3" "1" "小刚"
"4" "2" "小华"
"5" "3" "小强"
"6" "3" "小四"
"7" "1" "小刘"
"8" "1" "小花"
选择student_table 所有数据
SELECT * FROM student_table;
ID class name
"1" "1" "小明"
"2" "2" "小红"
"3" "1" "小刚"
"4" "2" "小华"
"5" "3" "小强"
"6" "3" "小四"
"7" "1" "小刘"
"8" "1" "小花"
通过GROUP选择不重复的班级
SELECT * FROM student_table GROUP BY class;
ID class name
"1" "1" "小明"
"2" "2" "小红"
"5" "3" "小强"
通过GROUP选择不重复的班级
SELECT class FROM student_table GROUP BY class;
class
"1"
"2"
"3"
按照班级、对班级进行计数
SELECT class,COUNT(class) FROM student_table GROUP BY class;
class COUNT(class)
1 4
2 2
3 2
以上就是关于数据库的一些基本操作。
