计算X天内在不同表中输入了多少行的最有效方法？

Question

Given several tables, what is the best way to take a poll of row counts in the tables with where clauses included? I'd like to do it at once so it can be inserted into a table with a daily record of row counts.

tableA - count of all rows that fit condition 1, a specific column value X select count(*) from tableA where col1 = X

tableA - count of all rows that fit condition 2, a specific column value Y select count(*) from tableA where col2 = Y

These two are easily combined into:

select
(select count(*) from tableA where col1 = X) as 'X count',
(select count(*) from tableA where col2 = Y) as 'Y count'

But now I'd like to add in: tableB - count of all rows that were created within the last specified interval

select count(*) from tableB where dateCreated >= date_sub(curdate(), interval 1 day) where col3 = Z;

This gives me:

select
(select count(*) from tableA where col1 = X) as 'X count',
(select count(*) from tableA where col2 = Y) as 'Y count',
(select count(*) from tableB where dateCreated >= date_sub(curdate(), interval 1 day)) as 'Z count';

It seems to run very slowly though, is there a more efficient way of counting rows in this case?

Answer 1

Your query looks fine, but you should index on those columns. To do so, from the documentation :

CREATE INDEX idx_col1 ON tableA (col1);
CREATE INDEX idx_col2 ON tableA (col2);
CREATE INDEX idx_dateCreated on tableB (dateCreated);