MySQL Learning experience 2

1tinyint small~ medium~ int big~ float double Dec (m,d) fixed-point number range is determined by MD for bit (M) bit type bit (1) bit (64).

2zerofill padding 0 such as ALTER TABLE T1 modify ID1 int zerofill;1 becomes 000001 the assumption is that int (6) in the case of INT (6) you enter 8 digits and do not stage Zerofill will automatically add UNS to the column change IGN Properties

3auto_increment can be used when generating unique identifiers and sequential values.

such as CREATE TABLE AI (id INT auto_increment not NULL, PRIMARY KEY (id));

or create TABLE AI (ID INT auto_increment not NULL PRIMARY KEY);

CREATE TABLE AI (id INT auto_increment not NULL, UNIQUE (ID));

4 fixed-point number in MySQL string storage is more precise than floating-point number m stands for M-digits (integer + decimal) d is the number after the decimal point, also known as precision and scale

5mysql when the value is saved to rounding such as float (7,4) Insert 999.00009 get 999.0001 dec at unspecified precision when default to (10,0) in traditional SQL beyond the qualified data cannot be inserted Dec MySQL will alarm

The 6bit field can be used to view the Select Bin (id) in bin () and Hex (), Hex (ID) from T2, and inserting data in fields with insufficient number of bits is not feasible.

MySQL Learning experience 2