多手资料，仅记录：
- PK: primary key (column is part of a pk)  主键
- NN: not null (column is nullable)  是否为空
- UQ: unique (column is part of a unique key)  外键
- AI: auto increment (the column is auto incremented when rows are inserted)  自动增加
-  BIN: binary (if dt is a blob or similar, this indicates that is binary data, rather than text)   二进制
- UN: unsigned (for integer types, see docs: “10.2. Numeric Types”)
- ZF: zero fill (rather a display related flag, see docs: “10.2. Numeric Types”)