MySQL database (on)
MySQL data types: numeric types, date and time, strings
1, numeric type
NOTE: BIT stored bit data type field value, and supports MyISAM, MEMORY, InnoDB and BDB tables
| Types of | size | Range (signed) | Range (unsigned) | use |
|---|---|---|---|---|
| TINYINT | 1 byte | (-128，127) | (0，255) | Small integer values |
| SMALLINT | 2 bytes | (-32 768，32 767) | (0，65 535) | Large integer values |
| MEDIUMINT | 3 bytes | (-8 388 608，8 388 607) | (0，16 777 215) | Large integer values |
| INT or INTEGER | 4 bytes | (-2 147 483 648，2 147 483 647) | (0，4 294 967 295) | Large integer values |
| BIGINT | 8 bytes | (-9,223,372,036,854,775,808，9 223 372 036 854 775 807) | (0，18 446 744 073 709 551 615) | Maximum integer value |
| FLOAT | 4 bytes | (E + -3402 823 466 38 494 351 -1175 E-38) 0, (E-1175 494 351 823 466 351 E 38,3.402 + 38) | 0 (E-1175 494 351 823 466 38,3.402 E + 38) | Single-precision floating-point value |
| DOUBLE | 8 bytes | (-1,797 693 134 862 315 7 E + 308, -2 225 073 858 507 201 308 E-4) 0 (2,225 073 858 507 201 4 E-308,1.797 693 134 862 315 7 E + 308) | 0 (2,225 073 858 507 201 4 E-308,1.797 693 134 862 315 7 E + 308) | Double-precision floating-point values |
| DECIMAL | Of DECIMAL (M, D), if M> D, M + 2 is otherwise D + 2 | Depending on the value of M and D | Depending on the value of M and D | Small value |
2, the date and time types
Note: Each time type has a value range of valid values and a "zero" value of "zero" when the value of the specified unlawful MySQL can not be represented.
| Types of | Size (bytes) |
range | format | use |
|---|---|---|---|---|
| DATE | 3 | 1000-01-01/9999-12-31 | YYYY-MM-DD | Date values |
| TIME | 3 | '-838:59:59'/'838:59:59' | HH:MM:SS | Time value or duration |
| YEAR | 1 | 1901/2155 | YYYY | Year Value |
| DATETIME | 8 | 1000-01-01 00:00:00/9999-12-31 23:59:59 | YYYY-MM-DD HH:MM:SS | Date and time value mixing |
| TIMESTAMP | 4 | 1970-01-01 00:00:00/2038 End times are 2147483647 seconds, the Beijing 2038-1-19 11:14:07 GMT, January 19, 2038 early morning 03:14:07 |
YYYYMMDD HHMMSS | Mixing date and time value, the time stamp |
3, character string type
Note: 1, BINARY and VARBINARY similar to CHAR and VARCHAR, except that they contain binary strings rather than non-binary strings. That is, they contain byte strings rather than character strings . This is that they have no character set , and sorting and comparison is based on column values numeric value byte . BINARY keyword is case sensitive.
| Types of | size | use |
|---|---|---|
| CHAR | 0-255 bytes | Fixed-length string |
| VARCHAR | 0-65535 bytes | Variable-length strings |
| TINYBLOB | 0-255 bytes | No more than 255 characters in binary string |
| BLOB | 0-65535 bytes | Long text data in binary form |
| MEDIUMBLOB | Bytes 0-16777215 | Binary text data in the form of medium length |
| LONGBLOB | 0-4294967295 bytes | Great text data in binary form |
| TINYTEXT | 0-255 bytes | Short text strings |
| TEXT | 0-65535 bytes | Long text data |
| MEDIUMTEXT | 0-16777215 bytes, | Medium length text data |
| LONGTEXT | 0-4294967295 bytes | Great text data |
MySQL create data tables, query data table data for the table to sort the data in the data
First, the structure of the table:
1, the data table: table name, the table column (column), row (database record), index (Index is a table, which holds the primary key index field, and point recording entity table), the default value ( DEFAULT)
2、表中的列（column）字段名（column_name）和字段属性（column_type）：数据类型、“索引”（primary key、unique、index）、AI（自增，具有AI属性的列必须要建索引且该列的值必须是唯一的）、“约束”（BIN-二进制数据、UN-无符号数据、ZF-zero fill 填充0）
二、数据表操作指令
0、创建和选择数据库（database）
mysql> CREATE DATABASE RUNOOB； mysql> use RUNOOB；
1、创建指令，（在MySQL控制台，; 是命令终止符 、 -> 是换行符标识，enter键换行）
mysql> CREATE TABLE runoob_tbl( -> runoob_id INT NOT NULL AUTO_INCREMENT, -> runoob_title VARCHAR(100) NOT NULL, -> runoob_author VARCHAR(40) NOT NULL, -> submission_date DATE, -> PRIMARY KEY ( runoob_id ) -> )ENGINE=InnoDB DEFAULT CHARSET=utf8;
2、查看数据表指令
# 查看数据库中所有的数据表 mysql>show tables； # 查看数据库中表名为stations的数据表 mysql>desc stations；
3、删除数据表
# 删除数据库中的数据表
mysql>DROP TABLE runoob_tbl；
4、数据表中的数据发生变化
4.1、向数据表中特定的列插入数据
mysql> INSERT INTO runoob_tbl
-> (runoob_title, runoob_author, submission_date)
-> VALUES
-> ("学习 PHP", "菜鸟教程", NOW());
4.2、更新数据表中的数据
UPDATE table_name SET field1=new-value1, field2=new-value2 [WHERE Clause]
4.3、删除数据表中的数据
DELETE FROM table_name [WHERE Clause]
5、select查询数据表数据
5.1、读取数据表信息
mysql> select * from runoob_tbl;
5.2、使用where语句查询数据表中的数据。WHERE 子句的字符串比较是不区分大小写的，可以使用 BINARY 关键字来设定 WHERE 子句的字符串比较是区分大小写的。
SELECT column_name,column_name FROM table_name（table_name1, table_name2...） [WHERE Clause（condition1 [AND [OR]] condition2.....）] [LIMIT N][ OFFSET M]
注：
1、可以使用一个或者多个表，表之间使用逗号(,)分割
2、WHERE语句设定查询条件
3、LIMIT 属性来设定返回的记录数
4、OFFSET指定SELECT语句开始查询的数据偏移量。默认情况下偏移量为0
5.3、使用'like'语句作为where的字句，用百分号 %字符来表示任意字符
mysql> SELECT * from runoob_tbl WHERE runoob_author LIKE '%COM';
5.4、使用union语句查询多个数据表的数据并删除重复数据；union ALL语句查询多个数据表的数据并返回重复数据
SELECT country FROM Websites UNION SELECT country FROM apps ORDER BY country;
SELECT country, name FROM Websites WHERE country='CN' UNION ALL SELECT country, app_name FROM apps WHERE country='CN' ORDER BY country;
6、利用order by 字句将select查询数据表数据排序之后再返回
SELECT field1, field2,...fieldN FROM table_name1, table_name2... ORDER BY field1 [ASC [DESC][默认 ASC]], [field2...] [ASC [DESC][默认 ASC]]
注：
1、ASC表示升序排序，DESC表示降序排列
2、可以设定多个字段来排序
7、GROUP BY语句根据一个或多个列的结果集进行分组，function可以是COUNT, SUM, AVG等函数,coun(*)：计算有多少条记录，sum（column_name） as column_name_count
SELECT column_name, function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name;
统计每个name有多少条记录
mysql> SELECT name, COUNT(*) FROM employee_tbl GROUP BY name;
WITH ROLLUP 可以实现在分组统计数据基础上再进行相同的统计（SUM,AVG,COUNT…）；coalesce 可以取代 NUll 的名称
mysql> SELECT name, SUM(singin) as singin_count FROM employee_tbl GROUP BY name WITH ROLLUP;
mysql> SELECT coalesce(name, '总数'), SUM(singin) as singin_count FROM employee_tbl GROUP BY name WITH ROLLUP;