Tips for Mixing OR and AND in SQL Statements

Today, there is such a requirement. If the logged-in person is a customer service representative, the order will be queried for "this customer service representative" and the orders that have not been matched with a customer service representative. At first, I thought of spelling "or assigned_id is null" directly in the SQL statement. After testing, I found that in this case, the other previous conditions are useless.

In this case, the first condition i.server_org_id = 4 is no longer applicable. From this we can see that AND has a higher priority than OR. The previous AND statement is executed first, and then the following OR statement is executed. Therefore, the data retrieved is not the data I want.

Later I thought about it again and found that I could first find out the corresponding assigned_id, as follows

The only data found in this way is the assigned_id 153

Final version:

Finally, all the correct data is read out. From this, we can see that () has a higher priority than AND. () is executed first, and then AND is executed.

The above is the full content of this article. I hope it will be helpful for everyone’s study. I also hope that everyone will support 123WORDPRESS.COM.