mysql--Data integrity

-Data type principle try to use a small range of values to save storage space integer: int, bit decimal: decimal denotes floating-point number decimal (5, 2) a total of 5 digits, and decimals is a 2-bit string: varchar (variable-length string), char (fixed-length string) date Room: Date, Time, datetime enum type (enum) attached: string text means storing large text, characters greater than 4000 recommended for picture Audio video and other large files, not stored in the database-constrained primary key: Primary key physically stored in order Non-null: The unique field does not allow duplicate defaults: default does not fill in defaults, fill in to fill in as the quasi foreign key: FOREIGN key FOREIGN KEY constraint can guarantee data validity, but in the data additions and deletions to reduce the performance of the database, is not recommended to use

mysql--Data integrity