To get the Max and Min value of a column for each day in MYSQL with a WHERE clause:

SELECT DATE(t.datetimecol), MAX(t.col1), MIN(t.col2) FROM TABLENAME t WHERE id = 1 GROUP BY DATE(t.datetimecol)

With no WHERE clause:

SELECT DATE(t.datetimecol), MAX(t.col1), MIN(t.col2) FROM TABLENAME t GROUP BY DATE(t.datetimecol)

Remember to actually put in your column and table names….

This will output like this: