About MySQL transaction row lock forupdate to realize write lock function

In E-commerce, there will often be a small number of inventory, the purchase of the person is particularly large, concurrency in the case of how to ensure that the number of goods will not be purchased multiple times.

In fact very simple, use the transaction +for update can be solved.

We all know that for update is actually a shared lock that can be read. But how to execute it without being read.

To put it simply: Assuming inventory is now 1, now there is a and B at the same time purchase

Open a transaction first

Begin

Select the good where id=1 for update;//query Good the number of stock in a product

After checking out, in the program to determine whether the stock is 0 (what language you use, not my business)

Finally in the implementation

Update good set stock=stock-1 where id=1

Finally in

Commit

But this time B is also select the stock from good where id=1 for update; Note: For update cannot omit ... This time will appear to be locked, unable to be read.

So this will ensure that the number of goods remaining 1 of the consistency.