MySQL's learning essay Day1

Basic statement about MySQL

Ps:[] is the default

Created: Create DATABASE db.name

CREATE table name (column name, type, [NULL]) NOT NULL is not required to be empty, not NULL needs to be defined when TABLE is created

Select database: Use Db.name

Show current database: SELECT database ()

Show now exists: Show DATABASES

SHOW TABLES [from Db.name]

Show table data structure: show COLUMNS from Tb.name

Insert record (data): Insert[into] tb.name [(Col.name,...)] VALUES (Val,...)

PRIMARY KEY constraint PRIMARY key has uniqueness, each table can have only one primary key, not NULL

Uniqueness of unique constraint exists, there can be more than one unique in a table, can be NULL, but null in a table can only have one

Default constraint defaults is set default value

Auto-encode (applies int, but can use floating-point number, but not decimal) auto_increment can only be bound on primary key (when the primary key is similar ID, it is convenient to use automatic encoding)

Show Table records: SELECT * from Table.name

MySQL's learning essay Day1