MySQLLesson01

ISO SQL：2003 standard data types

Character String TypesNational Character String TypesBinary Large Object String TypesNumeric TypesBoolean TypesDatetime TypesInterval Types

SQL:2003-string types

Fixed-width strings: CHARACTER(length)CHAR(length)Variable-length strings: CHARACTER VARYING(length)CHAR VARYING(length)VARCHAR(length)Character objects: CHARACTER LARGE OBJECTCHAR LARGE OBJECTCLOB

String Data Types in mysql

CHAR and VARCHAR

BINARY and VARBINARY

BLOB and TEXTENUMSET

CHAR and VARCHAR

Declare Char(N) 　　     0 to 255Varchar(N)        0 to 65,535Difference StoredRetrievedmaximum length

sql_mode

SET sql_mode = ''; --defaultSET sql_mode = 'PAD_CHAR_TO_FULL_LENGTH';SET sql_mode = 'STRICT_ALL_TABLES';SET sql_mode = 'STRICT_ALL_TABLES,ERROR_FOR_DIVISION_BY_ZERO';SET sql_mode = 'STRICT_ALL_TABLES,NO_ZERO_DATE,NO_ZERO_IN_DATE';SET sql_mode = 'ALLOW_INVALID_DATES';SET sql_mode = 'STRICT_ALL_TABLES,ALLOW_INVALID_DATES';

 

查看sql_mode:

①show variables like 'sql_mode';

设置sql_mode:

①set sql_mode = '';

求长度

①select length(col1),length(col2) from table_name;

查看表结构的命令

①desc table_name;

②explain table_name;

③show columns from table_name;

查看表的确切定义

①show create table table_name;

删除某一列

①alter table table_name drop column_name;

转载于:https://www.cnblogs.com/JayZhu/p/4472533.html