[intrinsic column flags] (基本字段类型标识)
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
[additional data type flags, depend on used data type] 扩展数据类型标记
BIN: Is binary column (if data is a blob or similar, this indicates that is binary data, rather than text) 存放二进制数据的列
UN: unsigned (for integer types, see docs: “10.2. Numeric Types”) 无符号整数
ZF: Fill up values for that column with 0's if it is numeric (rather a display related flag, see docs: “10.2. Numeric Types”)填充0位（例如指定3位小数，整数18就会变成18.000）
mysql
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