记录
插入记录
INSERT [ INTO ] tb_name [ (col_name,...)] {VALUES | VALUE}
({expr | DEFAULT} ,...) , (...) , ...;INSERT [INTO] tb_name SET col_name = { expr | DEFAULT } , ...INSERT [INTO] tb_name [(col_name,...) SELECT ...eg.：
INSERT test VALUES('max',13,1000);INSERT test(username) SELECT username FROM users WHERE age >=30;查找记录
查询表达式（select_expr）
SELECT select_expr [,select_expr ...]
[
FROM table_references
[WHERE where_condition]
[GROUP BY {col_name | position} [ ASC | DESC],...]
[HAVING where_condition]
[ORDER BY {col_name | expr | position} [ASC | DESC],...]
[LIMIT {[offset,] row_count | row_count OFFSET offset }]
]- 星号（*）表示所有
- 查询表达式可用 [AS] alias_name 赋予别名，可用于 GROUP BY ，ORDRE BY ，HAVING
- GROUP BY 查询结果分组ASC升序，DESC降序
- HAVING 分组设置条件
- ORDER BY 对查询结果进行排序
- LIMIT 限制返回查询结果的数量
eg.：#没有WHERE语句，则默认选择所有
SELECT * FROM test;
SELECT sex FROM users GROUP BY sex;
SELECT sex,age FROM users GROUP BY sex HAVING age > 18;
SELECT * FROM users ORDER BY id DESC;
SELECT * FROM users LIMIT 2;
SELECT * FROM users LIMIT 2,2; #从0开始，第一个2是从第三开始查询
SELECT goods_id,goods_name FROM tdb_goods GROUP BY goods_name HAVING count(good_name) >=2 ;
子查询（Sub Query）:
- 另一个查询语句中的SELECT子句
- 必须在圆括号里面
- 外查询可以是SELECT，INSERT，UPDATE，SET，DO
- 返回标量、一行、一列、子查询
- 比较运算符 != >= <= = < > <=> <>
SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2);\G;#记录显示
SET NAMES gbk;
更新记录
单表更新
UPDATE [LOW_PRIORITY][IGNOGE] table_reference SET
col_name1 = {expr1 | DEFAULT} [, col_name2 = { expr2 | DEFAULT }]...
[WHERE where_condition]多表更新
UPDATE table_references
SET col_name1 = {expr1|DEFAULT}
[,col_name2 = {expr2|DEFAULT}] ...
[WHERE where_condition]
//更新多表
UPDATE tdb_goods INNER JOIN tdb_goods_cates ON good_cate = cate_name
SET goods_cate = cate_id;创建表时，将查询结果写入表
CREATE TABLE [IF NOT EXISTS] tbl_name
[(create_definition,...)]
select_statement//创建时,填入查询结果
CREATE TABLE tdb_goods_brands
(
brand_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
brand_name VARCHAR(40) NOT NULL
)
SELECT brand_name FROM tdb_goods GROUP BY brand_name;删除记录
DELETE FROM tb_name [WHERE where_condition]多表删除
DELETE tbl_name[.*][,tbl_name[.*]]...
FROM table_references
[WHERE where_condition]//删除重复
DELETE t1 FROM tdb_goods AS t1 LEFT JOIN (
SELECT goods_id,goods_name FROM tdb_goods GROUP BY goods_name
HAVING count(good_name) >=2 ) AS t2
ON t1.goods_name = t2.goods_name
WHERE t1.goods_id > t2.goods_id;连接
table_reference
{[INNER | CROSS] JOIN | {LEFT |RIGHT} [OUTER] JOIN}
table_reference
ON conditional_expr//多表连接
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods
AS g
INNER JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
INNER JOIN tdb_goods_brands AS b ON g.brand_id = b.brands_id\G;连接类型
MySQL中，JOIN，CROSS JOIN 和INNER JOIN是等价的
- INNER JOIN ,内连接:显示左、右表符合连接条件的记录
- LEFT [OUTER] JOIN ,左外连接:显示左表全部、右表符合条件的记录
- RIGHT [OUTER] JOIN ,右外连接:显示右表全部、左表符合条件的记录
连接条件
- 使用ON设定连接条件
- 使用WHERE进行结果的过滤
//查询所有商品的详细信息
内连接
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g
INNER JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
INNER JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;左外连接
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g
LEFT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
LEFT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;右外连接
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g
RIGHT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
RIGHT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;无限级分类表
CREATE TABLE tdb_goods_types(
type_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
type_name VARCHAR(20) NOT NULL,
parent_id SMALLINT UNSIGNED NOT NULL DEFAULT 0
); 自身连接：对自己进行连接
//查询目前父类名字、子类id名字（一级查询）
SELECT s.type_id,s.type_name,p.type_name FROM tdb.goods_types
AS s LEFT JOIN tdb_goods_types AS p
ON s.parent_id = p.type_id;数据表参照
table_reference
tbl_name [[AS] alias] | table_subquery [AS] alias数据表可以使用赋予别名
- tbl_name AS alias_name
- tbl_name alias_name
table_subquery可以作为子查询使用在FROM子句中,这样的子查询必须为其赋予别名