Nested case statement in MYSQL

Question

SELECT CREX.RECODE,
(CASE WHEN ARX.ARRATE <> 0 THEN
    ARX.ARRATE
ELSE
    (CASE WHEN SBX.SBCLBL-SBX.SBDRBL > ARX.ARAMT1 THEN
        (CASE WHEN SBX.SBCLBL-SBX.SBDRBL > ARX.ARAMT2 THEN
            (CASE WHEN SBX.SBCLBL-SBX.SBDRBL > ARX.ARAMT3 THEN
                (CASE WHEN SBX.SBCLBL-SBX.SBDRBL > ARX.ARAMT4 THEN
                    (CASE WHEN SBX.SBCLBL-SBX.SBDRBL > ARX.ARAMT5 THEN
                        (CASE WHEN SBX.SBCLBL-SBX.SBDRBL > ARX.ARAMT6 THEN
                        ELSE ARX.ARRAT6 END)
                    ELSE ARX.ARRAT5 END)
                ELSE ARX.ARRAT4 END)
            ELSE ARX.ARRAT3 END)
        ELSE ARX.ARRAT2 END)
    ELSE ARX.ARRAT1 END)
END) AS BUNGA,

ROW_NUMBER() OVER(PARTITION BY CREX.RECODE ORDER BY ARX.ARDTVL DESC) AS RN
FROM CTE_M5RE CREX
LEFT JOIN CORE_BMI.M6SB SBX ON (CREX.RECODE = SBX.SBRECO)
LEFT JOIN CORE_BMI.H8AR ARX ON (CREX.RECODE = ARX.ARRECO)

I'm writing an MySQL Query, where a few of the columns returned need to be calculated depending on quite a lot of conditions.

Anyone know how to fix my code?

Answer 1

I do suspect that your nested expressions can be simplified to something like:

CASE 
    WHEN ARX.ARRATE <> 0 THEN ARX.ARRATE
    WHEN SBX.SBCLBL - SBX.SBDRBL <= ARX.ARAMT1 THEN ARX.ARRAT1
    WHEN SBX.SBCLBL - SBX.SBDRBL <= ARX.ARAMT2 THEN ARX.ARRAT2
    WHEN SBX.SBCLBL - SBX.SBDRBL <= ARX.ARAMT3 THEN ARX.ARRAT3
    WHEN SBX.SBCLBL - SBX.SBDRBL <= ARX.ARAMT4 THEN ARX.ARRAT4
    WHEN SBX.SBCLBL - SBX.SBDRBL <= ARX.ARAMT5 THEN ARX.ARRAT5
    WHEN SBX.SBCLBL - SBX.SBDRBL <= ARX.ARAMT6 THEN ARX.ARRAT6
END AS BUNGA