COUNT() is selecting number of rows in table

Question

My COUNT(*) in the query below is selecting the count of the number of rows in the table users rather than the number of rows where distance is less than 50.

Please can you tell me why the query is selecting the number of rows in the table users rather than the number of rows where the distance is less than 50?

Thanks in advanced.

SELECT COUNT(*), ( 6371 * ACOS( COS( RADIANS( 51.61050836267012 ) ) * COS( RADIANS( latitude ) ) * COS( RADIANS( longitude ) - RADIANS( - 0.23701071739196777 ) ) + SIN( RADIANS( 51.61050836267012 ) ) * SIN( RADIANS( latitude ) ) ) ) 
AS distance
FROM  `users` 
AS `u`
HAVING distance <=50

Answer 1

HAVING should be related to GROUP BY expression. To restrict number of rows to a given criteria use WHERE distance <= 50

Answer 2

HAVING适用于聚合值（例如具有特定条件的sum（列））在您的情况下应该使用WHERE而不是HAVING

Answer 3

The having clause doesn't filter on rows like a where clause would for your count function. Try using a subquery instead.