学点SQL语句（一）-CFANZ编程社区

文章目录

库操作
表操作

库操作

语法：
增：CREATE DATABASE NAME;

create database d2;

查：
查看指定库：
SHOW CREATE DATABASE NAME；
查看所有库：
SHOW DATABASES；
查看当前库：
SELECT DATABASE();

show create database d2;
show databases;
show database();

选择数据库：
USE NAME;

use d2;

删：
DROP DATABASE NAME;

drop database d2;

改：
也就只能修改库的字符编码
ALTER DATABASE NAME CHARSET CHAR_CODE;

alter database name charset gbk;

mysql> create database d2;
Query OK, 1 row affected (0.12 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| d1                 |
| d2                 |
| mysql              |
| performance_schema |
| test               |
+--------------------+
6 rows in set (0.10 sec)

mysql> show create database d2;
+----------+-------------------------------------------------------------+
| Database | Create Database                                             |
+----------+-------------------------------------------------------------+
| d2       | CREATE DATABASE `d2` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+-------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| d1                 |
| d2                 |
| mysql              |
| performance_schema |
| test               |
+--------------------+
6 rows in set (0.00 sec)

mysql> select database;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
mysql> select database();
+------------+
| database() |
+------------+
| NULL       |
+------------+
1 row in set (0.00 sec)

mysql> alter database d2 charset gbk;
Query OK, 1 row affected (0.09 sec)

mysql> show create database d2;
+----------+------------------------------------------------------------+
| Database | Create Database                                            |
+----------+------------------------------------------------------------+
| d2       | CREATE DATABASE `d2` /*!40100 DEFAULT CHARACTER SET gbk */ |
+----------+------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> drop database d2;
Query OK, 0 rows affected (0.18 sec)

mysql> select database();
+------------+
| database() |
+------------+
| NULL       |
+------------+
1 row in set (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| d1                 |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)

mysql>

表操作

创建：
CREATE TABLE NAME(字段名1 类型[（宽度）约束条件]，字段名2 类型[（宽度）约束条件])；

create table t3(id int);
create table t4(id int,name char):

查:
查看所有表:
SHOW TABLES;
查看某一张表结构
SHOW CREATE NAME;
查看某一张表的详细结构
DESC NAME;
查看表内的所有记录：
SELECT * FROM NAME;
查看表内某一条记录：
SELECT NAME FROM NAME;

show tables;
show create table t1;
desc t1;
select * from t1;
select id from t1;

向表内插入记录：
INSERT INTO NAME VALUSES();
特定字段插入记录：
INSERT INTO NAME(NAME,NAME,NAME) VALUSES();

insert into  t1 values(7,'wang');
insert into  t1(id) values(5);

修改：
改表名：
ALTER TABLE NAME RENAME NEW_NAME
增加字段：
ALTER TABLE NAME ADD CHAR_NAME 数据类型,ADD CHAR_NAME 数据类型;
为增加的字段设定位置：
放首位：
ALTER TABLE NAME ADD CHAR_NAME 数据类型 FIRST;
放在xx后面：
ALTER TABLE NAME ADD CHAR_NAME 数据类型 AFTER 字段名；

alter table t1 rename t11;
alter table t11 add age int;
alter table t11 add sex char first;
alter table t11 add gender char after sex;

删除字段：
ALTER TABLE NAME DROP NAME;
修改字段：
ALTER TABLE NAME MODIFY NAME 数据类型;
ALTER TABLE NAME CHANGE NAME NEW_NAME 旧数据类型；
ALTER TABLE NAME CHANGE NAME NEW_NAME 新数据类型；

alter table t11 drop age;
alter table t11 modify name char;
alter table t11 change name Name char;
alter table t11 change Name name char(2);

复制表

复制表结构+记录
CREATE TABLE NEW_NAME SELECT * FROM NAME;
只复制表结构
CREATE TABLE NEW_NAME SELECT * FROM NAME WHER FALSE(1=2);

create table new_t1 select * from t11;
create table new_t11 select * from t11 where 1 >2

删除表
DROP TABLE NAME;

drop table new_t11;
drop table new_t111;

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| d1                 |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)

mysql> use d1;
Database changed
mysql> show tables;
+--------------+
| Tables_in_d1 |
+--------------+
| new_t1       |
| t1           |
| t4           |
+--------------+
3 rows in set (0.10 sec)

mysql> show create table t1;
+-------+---------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                        |
+-------+---------------------------------------------------------------------------------------------------------------------+
| t1    | CREATE TABLE `t1` (
  `id` int(11) DEFAULT NULL,
  `name` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+-------+---------------------------------------------------------------------------------------------------------------------+
1 row in set (0.18 sec)

mysql> desc t1;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | YES  |     | NULL    |       |
| name  | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> create table t1(id int);
ERROR 1050 (42S01): Table 't1' already exists
mysql> create table t3(id int);
Query OK, 0 rows affected (1.00 sec)

mysql> show tables;
+--------------+
| Tables_in_d1 |
+--------------+
| new_t1       |
| t1           |
| t3           |
| t4           |
+--------------+
4 rows in set (0.00 sec)

mysql> select * from t1;'
+------+------+
| id   | name |
+------+------+
|    1 | NULL |
|    2 | NULL |
|    1 |    0 |
|    1 |    1 |
+------+------+
4 rows in set (0.10 sec)

    '> \c
    '> /c
    '> '\c
mysql> select id from t1;
+------+
| id   |
+------+
|    1 |
|    2 |
|    1 |
|    1 |
+------+
4 rows in set (0.00 sec)

mysql> insert into table t1 valuse(1,'wang');
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'table t1 valuse(1,'wang')' at line 1
mysql> insert into table t1 valuse(7,'wang');
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'table t1 valuse(7,'wang')' at line 1
mysql> insert into table t1 values(7,'wang');
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'table t1 values(7,'wang')' at line 1
mysql> insert into t1 values(1,'wang');
Query OK, 1 row affected, 1 warning (1.83 sec)

mysql> desc t1;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | YES  |     | NULL    |       |
| name  | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> select * from t1;
+------+------+
| id   | name |
+------+------+
|    1 | NULL |
|    2 | NULL |
|    1 |    0 |
|    1 |    1 |
|    1 |    0 |
+------+------+
5 rows in set (0.00 sec)

mysql> insert into t1 values(7,2);
Query OK, 1 row affected (1.84 sec)

mysql> select * from t1;
+------+------+
| id   | name |
+------+------+
|    1 | NULL |
|    2 | NULL |
|    1 |    0 |
|    1 |    1 |
|    1 |    0 |
|    7 |    2 |
+------+------+
6 rows in set (0.00 sec)

mysql> inset into t1(id) values(5);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'inset into t1(id) values(5)' at line 1
mysql> insert into t1(id) values(5);
Query OK, 1 row affected (0.25 sec)

mysql> select * from t1;
+------+------+
| id   | name |
+------+------+
|    1 | NULL |
|    2 | NULL |
|    1 |    0 |
|    1 |    1 |
|    1 |    0 |
|    7 |    2 |
|    5 | NULL |
+------+------+
7 rows in set (0.00 sec)

mysql> alter table t1 rename t11;
Query OK, 0 rows affected (2.16 sec)

mysql> show tables;
+--------------+
| Tables_in_d1 |
+--------------+
| new_t1       |
| t11          |
| t3           |
| t4           |
+--------------+
4 rows in set (0.00 sec)

mysql> alter table t11 add agg(int);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(int)' at line 1
mysql> alter table t11 add age int;
Query OK, 0 rows affected (3.21 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> select * from t11;
+------+------+------+
| id   | name | age  |
+------+------+------+
|    1 | NULL | NULL |
|    2 | NULL | NULL |
|    1 |    0 | NULL |
|    1 |    1 | NULL |
|    1 |    0 | NULL |
|    7 |    2 | NULL |
|    5 | NULL | NULL |
+------+------+------+
7 rows in set (0.00 sec)

mysql> alter drop age;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'drop age' at line 1
mysql> alter t11 drop age;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 't11 drop age' at line 1
mysql> alter table t11 drop age;
Query OK, 0 rows affected (2.47 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> select * from t11;
+------+------+
| id   | name |
+------+------+
|    1 | NULL |
|    2 | NULL |
|    1 |    0 |
|    1 |    1 |
|    1 |    0 |
|    7 |    2 |
|    5 | NULL |
+------+------+
7 rows in set (0.00 sec)

mysql> alter table t11 name char;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'name char' at line 1
mysql> alter table t11 modify name char;
Query OK, 7 rows affected (3.61 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> select * from t11;
+------+------+
| id   | name |
+------+------+
|    1 | NULL |
|    2 | NULL |
|    1 | 0    |
|    1 | 1    |
|    1 | 0    |
|    7 | 2    |
|    5 | NULL |
+------+------+
7 rows in set (0.00 sec)

mysql> desc t11;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | YES  |     | NULL    |       |
| name  | char(1) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> alter table t11 change name Name char;
Query OK, 0 rows affected (0.26 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc
    -> t11;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | YES  |     | NULL    |       |
| Name  | char(1) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> alter table t11 change Name name char(2);
Query OK, 7 rows affected (1.98 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> desc t11;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | YES  |     | NULL    |       |
| name  | char(2) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> create table new_t1 select * from t11;
ERROR 1050 (42S01): Table 'new_t1' already exists
mysql> create table new_t11 select * from t11;
Query OK, 7 rows affected (0.94 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> desc new_t11;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | YES  |     | NULL    |       |
| name  | char(2) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> create table new_t111 select * from t11 where 1=2;
Query OK, 0 rows affected (0.55 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc new_t111;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | YES  |     | NULL    |       |
| name  | char(2) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> select * from new_t11;
+------+------+
| id   | name |
+------+------+
|    1 | NULL |
|    2 | NULL |
|    1 | 0    |
|    1 | 1    |
|    1 | 0    |
|    7 | 2    |
|    5 | NULL |
+------+------+
7 rows in set (0.00 sec)

mysql> select * from new_t111;
Empty set (0.00 sec)

mysql> show tables;
+--------------+
| Tables_in_d1 |
+--------------+
| new_t1       |
| new_t11      |
| new_t111     |
| t11          |
| t3           |
| t4           |
+--------------+
6 rows in set (0.00 sec)

mysql> drop new_t1;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'new_t1' at line 1
mysql> dw_t1;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'dw_t1' at line 1
mysql>
mysql> drop table new_t1;
Query OK, 0 rows affected (1.52 sec)

mysql> drop table new_t11;
Query OK, 0 rows affected (0.64 sec)

mysql> drop table new_t111;
Query OK, 0 rows affected (0.65 sec)

mysql> show tables;
+--------------+
| Tables_in_d1 |
+--------------+
| t11          |
| t3           |
| t4           |
+--------------+
3 rows in set (0.00 sec)

mysql>