(explanatory text) Relationship between primary key 0 and primary key self-draining constraints in My SQL

The last one we said about self-draining if the primary key is 0, here I figure out why, cause this is because the initial value is set in SQL for the self-row:

　　

From here you can see that the two variables, one is the increment of the initial value, one is incremental, here is 1, so when the setting of self-increment will be that field of the original existence of all 0 to the beginning of the 1 step 1 of the arithmetic progression.　　However, this value can be modified (but not recommended here), if the insert is inserted at the time of 0, it will default to insert the line number, or the default value automatically becomes the line number. First we have to understand that the primary key from the row, why to use the primary key self-platoon, not because of the subsequent indexing and other convenient operation, so here will be inserted with the line number to change 0 completely reasonable.

(explanatory text) Relationship between primary key 0 and primary key self-draining constraints in My SQL