SELECT inside IF statement - mysql

Question

SELECT jargons.jargon as jargon,
jargons.description as description,
jargons.example as example,
IF(jargons.rootJargon != 0, (SELECT jargon FROM jargons WHERE id = jargons.rootJargon), NULL) as rootJargonName
FROM jargons
LEFT JOIN users ON users.id = jargons.addedBy
ORDER BY jargons.id DESC
I have two rows inside jargons table:
"id" "jargon" "description" "example" "rootJargonName" "rootJargon"
"2" "Child" "jd" "1" NULL 1
"1" Root" "sad" "1" NULL 0
Why does the rootJargonName returns null instead of Root on Child row?
What I was trying to do is that if rootJargon column is not equals to zero then select the row with the id that specified in the column which is not equals to zero.

Answer 1

It's likely a table alias issue you're seeing, but you can rewrite this using a LEFT JOIN:
SELECT J.jargon as jargon,
J.description as description,
J.example as example,
R.jargon As rootJargonName
FROM jargons as J
LEFT JOIN users as U ON U.id = J.addedBy
LEFT JOIN jargons as R ON J.rootJargon = R.ID
ORDER BY J.id DESC
If you would like to keep the IF() function, you can use the following, however I recommend using the LEFT JOIN.
SELECT J.jargon as jargon,
J.description as description,
J.example as example,
IF(J.rootJargon != 0, (SELECT jargon FROM jargons as R WHERE R.id = J.rootJargon), NULL) as rootJargonName
FROM jargons as J
LEFT JOIN users as U ON U.id = J.addedBy
ORDER BY J.id DESC

Answer 2

why dont you try a case
like:
SELECT jargons.jargon as jargon,
jargons.description as description,
jargons.example as example,
CASE
WHEN (jargons.rootJargon == 0) THEN NULL
WHEN (jargons.rootJargon != 0) THEN
(SELECT jargon FROM jargons WHERE id = jargons.rootJargon)
END) AS 'rootJargonName'
FROM jargons
LEFT JOIN users ON users.id = jargons.addedBy
ORDER BY jargons.id DESC
I'm probably wrong somewhere in the syntax but i think thats the idea....