What does the := operator mean in mysql?

Question

I have a mysql table (scho_id,school_name,school_views).

I was looking for a mysql query to get

Answer 1

In MySQL, := is an assignment operator:

SELECT @foo := 'bar';    // variable 'foo' now has value 'bar'
return value: 'bar'

while = is an equality test:

SELECT @foo = 'hi mom'; // does variable 'foo' have the value 'hi mom';
return value: false   ('bar' == 'hi mom' -> false)

Note that you CAN do both equality testing AND assignment with set queries:

SET @foo = 'bar' = 'baz';

which will cause @foo to be assigned false, the boolean result of 'bar' = 'baz'. It executes as the following:

SET @foo = ('bar' = 'baz');
SET @foo = false;