• Mysql与其他数据库一些不同地方



    1.Insert Set语句
    mysql> create table wison_test1(id int,name varchar(10));
    Query OK, 0 rows affected (0.10 sec)

    mysql> insert into wison_test1 set id=1,name='wison';-------相对于后一条insert语句,返回的提示信息少了一行
    Query OK, 1 row affected (0.08 sec)

    mysql> select * from wison_test1;
    +------+-------+
    | id | name |
    +------+-------+
    | 1 | wison |
    +------+-------+
    1 row in set (0.00 sec)

    mysql> insert into wison_test1 select 2,'Wison';
    Query OK, 1 row affected (0.10 sec)
    Records: 1 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test1;
    +------+-------+
    | id | name |
    +------+-------+
    | 1 | wison |
    | 2 | Wison |
    +------+-------+
    2 rows in set (0.00 sec)
    2.数据类型带长度
    mysql> create table wison_test2(id int(5));
    Query OK, 0 rows affected (0.12 sec)

    mysql> insert into wison_test2 select 1;
    Query OK, 1 row affected (0.10 sec)
    Records: 1 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test2;
    +------+
    | id |
    +------+
    | 1 |
    +------+
    1 row in set (0.00 sec)

    mysql> alter table wison_test2 modify id int(5) zerofill;
    Query OK, 1 row affected (0.58 sec)
    Records: 1 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test2;
    +-------+
    | id |
    +-------+
    | 00001 |
    +-------+
    1 row in set (0.00 sec)

    mysql> insert into wison_test2 select 1111111;
    Query OK, 1 row affected (0.10 sec)
    Records: 1 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test2;
    +---------+
    | id |
    +---------+
    | 00001 |
    | 1111111 |
    +---------+
    2 rows in set (0.00 sec)
    3.BIT类型---直接读取会查询不出结果,需要使用hex()或者bin()
    mysql> create table wison_test3(id bit(2));
    Query OK, 0 rows affected (0.11 sec)

    mysql> insert into wison_test3 select 1;
    Query OK, 1 row affected (0.07 sec)
    Records: 1 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test3;
    +------+
    | id |
    +------+
    | |
    +------+
    1 row in set (0.00 sec)

    mysql> select hex(id) from wison_test3;
    +---------+
    | hex(id) |
    +---------+
    | 1 |
    +---------+
    1 row in set (0.00 sec)

    mysql> select bin(id) from wison_test3;
    +---------+
    | bin(id) |
    +---------+
    | 1 |
    +---------+
    1 row in set (0.00 sec)
    4.TIMESTAMP类型--在Mysql中会根据当前时区不同返回不同的值
    mysql> create table wison_test4(id1 timestamp,id2 datetime);
    Query OK, 0 rows affected (0.09 sec)

    mysql> show variables like 'time_zone';
    +---------------+--------+
    | Variable_name | Value |
    +---------------+--------+
    | time_zone | SYSTEM |
    +---------------+--------+
    1 row in set (0.00 sec)

    mysql> insert into wison_test4 select now(),now();
    Query OK, 1 row affected (0.07 sec)
    Records: 1 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test4;
    +---------------------+---------------------+
    | id1 | id2 |
    +---------------------+---------------------+
    | 2014-04-29 23:05:03 | 2014-04-29 23:05:03 |
    +---------------------+---------------------+
    1 row in set (0.00 sec)

    mysql> set time_zone='+9:00';
    Query OK, 0 rows affected (0.00 sec)

    mysql> select * from wison_test4;
    +---------------------+---------------------+
    | id1 | id2 |
    +---------------------+---------------------+
    | 2014-04-30 15:05:03 | 2014-04-29 23:05:03 |
    +---------------------+---------------------+
    1 row in set (0.00 sec)

    mysql> set time_zone='-7:00';
    Query OK, 0 rows affected (0.00 sec)

    mysql> select * from wison_test4;
    +---------------------+---------------------+
    | id1 | id2 |
    +---------------------+---------------------+
    | 2014-04-29 23:05:03 | 2014-04-29 23:05:03 |
    +---------------------+---------------------+
    1 row in set (0.00 sec)
    5.CHAR数据类型---CHAR会自动将后面的空格截断,VARCHAR会保留空格
    mysql> create table wison_test5(c1 char(5),c2 varchar(5));
    Query OK, 0 rows affected (0.11 sec)

    mysql> insert into wison_test5 select 'a ','a ';
    Query OK, 1 row affected (0.08 sec)
    Records: 1 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test5;
    +------+------+
    | c1 | c2 |
    +------+------+
    | a | a |
    +------+------+
    1 row in set (0.00 sec)

    mysql> select length(c1),length(c2) from wison_test5;
    +------------+------------+
    | length(c1) | length(c2) |
    +------------+------------+
    | 1 | 3 |
    +------------+------------+
    1 row in set (0.00 sec)

    mysql> select concat(c1,'+'),concat(c2,'+') from wison_test5;
    +----------------+----------------+
    | concat(c1,'+') | concat(c2,'+') |
    +----------------+----------------+
    | a+ | a + |
    +----------------+----------------+
    1 row in set (0.00 sec)
    6.ENUM类型---插入的值可以是在枚举的列表中,可以写明值,或者对应的顺序编号(比如3的意思就是第三个值),NULL(插入之后仍为NULL),传入不存在的值插入的是空格
    mysql> create table wison_test6(country ENUM('CN','US','TW','RU','BR'));
    Query OK, 0 rows affected (0.09 sec)
    mysql> insert into wison_test6 values ('CN'),('US'),('1'),('3'),('4'),(2),(NULL);
    Query OK, 7 rows affected (0.06 sec)
    Records: 7 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test6;
    +---------+
    | country |
    +---------+
    | CN |
    | US |
    | CN |
    | TW |
    | RU |
    | US |
    | NULL |
    +---------+
    7 rows in set (0.00 sec)

    mysql> insert into wison_test6 select 'CA';
    Query OK, 1 row affected, 1 warning (0.06 sec)
    Records: 1 Duplicates: 0 Warnings: 1

    mysql> show warnings;
    +---------+------+----------------------------------------------+
    | Level | Code | Message |
    +---------+------+----------------------------------------------+
    | Warning | 1265 | Data truncated for column 'country' at row 1 |
    +---------+------+----------------------------------------------+
    1 row in set (0.00 sec)

    mysql> select * from wison_test6;
    +---------+
    | country |
    +---------+
    | CN |
    | US |
    | CN |
    | TW |
    | RU |
    | US |
    | NULL |
    | |
    +---------+
    8 rows in set (0.00 sec)

    另一个例子----可以看到当枚举值背身为数字时,当insert的value没包含'',则表示是第几个枚举值,否则插入的值为insert的对应值.
    mysql> create table wison_test7(id ENUM('1','2','4','3','5'));
    Query OK, 0 rows affected (0.07 sec)

    mysql> insert into wison_test7 values('1'),('3'),(3),('4'),(4);
    Query OK, 5 rows affected (0.07 sec)
    Records: 5 Duplicates: 0 Warnings: 0

    mysql> select * from wison_test7;
    +------+
    | id |
    +------+
    | 1 |
    | 3 |
    | 4 |
    | 4 |
    | 3 |
    +------+
    5 rows in set (0.00 sec)

    7.在Mysql中,如果列上有索引,无需先Drop Index,可直接修改列。这点与MSSQL不一致。如下:

    mysql> create table test1(id int,name char(5));
    Query OK, 0 rows affected (0.30 sec)

    mysql> create index ix_test1_name on test1(name);
    Query OK, 0 rows affected (0.21 sec)
    Records: 0 Duplicates: 0 Warnings: 0

    mysql> show create table test1;
    +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
    | Table | Create Table |
    +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
    | test1 | CREATE TABLE `test1` (
    `id` int(11) DEFAULT NULL,
    `name` char(5) DEFAULT NULL,
    KEY `ix_test1_name` (`name`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
    +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
    1 row in set (0.00 sec)

    mysql> alter table test1 modify name char(10);
    Query OK, 0 rows affected (0.54 sec)
    Records: 0 Duplicates: 0 Warnings: 0

    mysql> show create table test1;
    +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
    | Table | Create Table |
    +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
    | test1 | CREATE TABLE `test1` (
    `id` int(11) DEFAULT NULL,
    `name` char(10) DEFAULT NULL,
    KEY `ix_test1_name` (`name`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
    +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
    1 row in set (0.00 sec)

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  • 原文地址:https://www.cnblogs.com/Wison-Ho/p/3701394.html
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