Having filtered result set

Source: Internet
Author: User

Title: allow you to output a list of students with two subjects and above (60-point pass)?

Name Subject Score

The wrong approach:

Mysql> select Name, Count (scoure<60) as GK from student group by name have GK >= 2;

Why would it be wrong?

Correct practice:

mysql> select name, sum (scoure<60) as GK from student group by name have GK >= 2;

Why is it wrong to use count? Because count () counts are counted as rows, he also doesn't care whether the section is hung or not. SUM () is sum, when less than 60 o'clock, is +1, greater than or equal to 60 o'clock is +0.

Having filtered result set

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