I got an error: #1242 - Subquery returns more than 1 row when i run this sql.
CREATE VIEW test
AS
SELECT cc_name,
COUNT() AS total,
(
SELECT COUNT()
FROM bed
WHERE respatient_id > 0
GROUP BY cc_name
You need to remove the group-by in the sub query, so possibly something like
SELECT COUNT(*)
FROM bed
WHERE respatient_id > 0
or possibly -- depending on what your application logic is....
SELECT COUNT(*) from (
select count(*),cc_name FROM bed
WHERE respatient_id > 0
GROUP BY cc_name) filterview
The problem is that your subselects are returning more than one value - IE:
SELECT ...
(SELECT COUNT(*)
FROM bed
WHERE respatient_id IS NULL
GROUP BY cc_name) AS free_beds,
...
...will return a row for each cc_name
, but SQL doesn't support compacting the resultset for the subselect - hence the error.
Don't need the subselects, this can be done using a single pass over the table using:
SELECT b.cc_name,
COUNT(*) AS total,
SUM(CASE
WHEN b.respatient_id > 0 THEN 1
ELSE 0
END) AS occupied_beds,
SUM(CASE
WHEN b.respatient_id IS NULL THEN 1
ELSE 0
END) AS free_beds
FROM bed b
GROUP BY b.cc_name
This is because your subqueries (the SELECT
bits that are inside parentheses) are returning multiple rows for each outer row. The problem is with the GROUP BY
; if you want to use subqueries for this, then you need to correlate them to the outer query, by specifying that they refer to the same cc_name
as the outer query:
CREATE VIEW test
AS
SELECT cc_name,
COUNT() AS total,
(SELECT COUNT()
FROM bed
WHERE cc_name = bed_outer.cc_name
AND respatient_id > 0) AS occupied_beds,
(SELECT COUNT(*)
FROM bed
WHERE cc_name = bed_outer.cc_name
WHERE respatient_id IS NULL) AS free_beds
FROM bed AS bed_outer
GROUP BY cc_name;
(See http://en.wikipedia.org/wiki/Correlated_subquery for information about correlated subqueries.)
But, as OMG Ponies and a1ex07 say, you don't actually need to use subqueries for this if you don't want to.
Your subqueries return more than 1 row. I think you you need something like :
SELECT COUNT(*) AS total,
COUNT(CASE WHEN respatient_id > 0 THEN 1 END) AS occupied_beds,
COUNT(CASE WHEN respatient_id IS NULL THEN 1 END) AS free_beds
FROM bed
GROUP BY cc_name
You can also try to use WITH ROLLUP
+ pivoting (mostly for learning purposes, it's a much longer query ) :
SELECT cc_name,
MAX(CASE
WHEN num_1 = 1 THEN tot_num END) AS free_beds,
MAX(CASE
WHEN num_1 = 2 THEN tot_num END) AS occupied_beds,
MAX(CASE
WHEN num_1 = IS NULL THEN tot_num END) AS total
FROM
(SELECT cc_name, CASE
WHEN respatient_id > 0 THEN 1
WHEN respatient_id IS NULL THEN 2
ELSE 3 END as num_1,
COUNT(*) as tot_num
FROM bed
WHERE
CASE
WHEN respatient_id > 0 THEN 1
WHEN respatient_id IS NULL THEN 2
ELSE 3 END != 3
GROUP BY cc_name,
num_1 WITH ROLLUP)A
GROUP BY cc_name