SQL

mysql get count of rows

SELECT COUNT(*) FROM my_table;
SELECT COUNT(*) FROM my_table WHERE my_column IS NULL;
SELECT COUNT(*) FROM my_table WHERE my_column = 'my_value';
SELECT COUNT(DISTINCT tel) gender_count,
       COUNT(DISTINCT CASE WHEN gender = 'male'   THEN tel END) male_count,
       COUNT(DISTINCT CASE WHEN gender = 'female' THEN tel END) female_count
FROM people;

mysql count rows returned

select count(*) from (select * from foo) as x;