MySQL建表时，PK.NN.UQ.AI.BIN.ZF的含义

PK: primary key (column is part of a pk) 主键

NN: not null (column is nullable) 非空

UQ: unique (column is part of a unique key) 唯一

AI: auto increment
(the column is auto incremented when rows are inserted) 自增

BIN: binary (if dt is a blob or similar, this indicates that is binary data,
rather than text) 二进制(比text更大的二进制数据)

UN: unsigned (for integer types, see docs: “10.2. Numeric Types”) 整数

ZF: zero fill
(rather a display related flag,
see docs: “10.2. Numeric Types”)值中最有意义的字节总为0，并且不保存。