mysql: retrieve all rows using common table expression - mysql

Question

i have this query which works but only gives the first five rows from the tables. see my former question -> multiple SELECT statements using CTE
WITH
cte AS ( SELECT n.name,
e.value,
ROW_NUMBER() OVER (PARTITION BY e.value
ORDER BY e.id) AS rn
from entries e
LEFT JOIN nodes n on n.id=e.node_id
LEFT JOIN attribs a on a.id=e.attrib_id
WHERE a.name = 'LOCATION'
AND e.value IN ('Wienerberg', 'Gruberstrasse')
AND DATE(ts) = CURRENT_DATE
ORDER BY e.id
),
nums AS ( SELECT 1 rn UNION
SELECT 2 UNION
SELECT 3 UNION
SELECT 4 UNION
SELECT 5
)
SELECT t1.name LNZ, t2.name WBG
FROM nums
LEFT JOIN cte t1 ON nums.rn = t1.rn
LEFT JOIN cte t2 ON nums.rn = t2.rn
WHERE t1.value = 'Gruberstrasse'
AND t2.value = 'Wienerberg'
-- AND COALESCE(t1.name, t2.name)
ORDER BY nums.rn
+----------------------+----------------------+
| LNZ | WBG |
+----------------------+----------------------+
| AIXVAEBDBT | KUG01148_JBOSS-T6 |
| OOEGKKT6 | AIXMVBMIGTA2 |
| HSR5S1P8_AM | KUG01115_WSAP_HA_LPM |
| AIXSTP11R3APP | AIXTESTHA2C1_HA_LPM |
| HSR3S1P10_OOEGKKTEST | KUG01142_STP17PR_HA |
+----------------------+----------------------+
how to i get all the rows without limiting to 5 rows? i skimmed through the mysql cte docs, but this seems to complex for me.

Answer 1

You are selecting from nums which will always return 5 rows.
Select from cte and make left join with nums.

Answer 2

You need 2 CTEs, for the 2 cases of 'Gruberstrasse' and 'Wienerberg' and then apply to them a simulated FULL JOIN (because MySql/MariaDB do not support a FULL JOIN):
WITH
cte1 AS ( SELECT n.name, e.value,
ROW_NUMBER() OVER (PARTITION BY e.value ORDER BY e.id) AS rn
FROM entries e
LEFT JOIN nodes n ON n.id = e.node_id
LEFT JOIN attribs a ON a.id = e.attrib_id
WHERE a.name = 'LOCATION' AND e.value = 'Gruberstrasse' AND DATE(ts) = CURRENT_DATE
),
cte2 AS ( SELECT n.name, e.value,
ROW_NUMBER() OVER (PARTITION BY e.value ORDER BY e.id) AS rn
FROM entries e
LEFT JOIN nodes n ON n.id = e.node_id
LEFT JOIN attribs a ON a.id = e.attrib_id
WHERE a.name = 'LOCATION' AND e.value = 'Wienerberg' AND DATE(ts) = CURRENT_DATE
)
SELECT c1.name LNZ, c2.name WBG
FROM cte1 c1 LEFT JOIN cte2 c2
ON c2.rn = c1.rn
UNION
SELECT c1.name LNZ, c2.name WBG
FROM cte2 c2 LEFT JOIN cte1 c1
ON c2.rn = c1.rn
Note that applying the condition:
a.name = 'LOCATION'
in the WHERE clause makes your LEFT join actually an INNER JOIN.
If the code works then fine, but if not then you should move this condition in the ON clause.
The same applies for the condition:
DATE(ts) = CURRENT_DATE
if ts is not a column of the table entries.

Answer 3

Before anything, since you're using MariaDB version above 10.1, you're in luck. MariaDB has such a thing called Storage Sequence Engine built-in. This thing can give you as many numbering sequence you want. So instead of doing:
SELECT 1 rn UNION
SELECT 2 UNION
SELECT 3 UNION
SELECT 4 UNION
SELECT 5
You can just do:
SELECT seq AS rn FROM seq_1_to_1000;
This will directly give you numbering sequence from 1 to 1000. Of course, you can add more than that and even using some other function than just running numbers. You can refer to the documentation link I've provided above.
The next thing I assume would be, "what if the rows are not even more than 100?". Like that, you don't need to change the numbering sequence but you can add another HAVING function at the end of the query, and maybe some IFNULL in the SELECT to replace NULL with some value.
Maybe something like this:
WITH
cte AS ( SELECT n.name,
e.value,
ROW_NUMBER() OVER (PARTITION BY e.value
ORDER BY e.id) AS rn
from entries e
LEFT JOIN nodes n on n.id=e.node_id
LEFT JOIN attribs a on a.id=e.attrib_id
WHERE a.name = 'LOCATION'
AND e.value IN ('Wienerberg', 'Gruberstrasse')
AND DATE(ts) = CURRENT_DATE
ORDER BY e.id
),
nums AS ( SELECT seq AS rn FROM seq_1_to_1000 )
SELECT IFNULL(t1.name,0) LNZ,
IFNULL(t2.name,0) WBG
FROM nums
LEFT JOIN cte t1 ON nums.rn = t1.rn
LEFT JOIN cte t2 ON nums.rn = t2.rn
WHERE t1.value = 'Gruberstrasse'
AND t2.value = 'Wienerberg'
-- AND COALESCE(t1.name, t2.name)
HAVING (0) NOT IN ('LNZ','WBG')
ORDER BY nums.rn;
Try this if it would work.
EDIT:
Here's another suggestion
SELECT Seq,
IFNULL(GROUP_CONCAT(CASE WHEN B.value='Gruberstrasse' THEN B.Name END),0) AS 'LNZ',
IFNULL(GROUP_CONCAT(CASE WHEN B.value='Wienerberg' THEN B.Name END),0) AS 'WBG'
FROM seq_1_to_1000 A LEFT JOIN
(SELECT n.name, e.value,
ROW_NUMBER() OVER (PARTITION BY e.value
ORDER BY e.id) AS rn
FROM entries e
LEFT JOIN nodes n ON n.id=e.node_id
LEFT JOIN attribs a ON a.id=e.attrib_id
WHERE a.name = 'LOCATION'
AND e.value IN ('Wienerberg', 'Gruberstrasse')
AND DATE(ts) = CURRENT_DATE
ORDER BY e.id) B
ON A.seq=B.rn GROUP BY A.seq
HAVING LNZ+WBG <> 0;
Without using cte:
LEFT JOIN the numbering sequence directly with the sub-query you originally made for the cte.
Using GROUP_CONCAT with CASE expression in SELECT then GROUP BY numbering sequence - added IFNULL to return zero and use that as filter in HAVING.