[not sure if this the correct category to post]
although there are some solutions for this…
what is, in your opinion, the fastest queries for this?..
C1 | C2 | C3 | C4
AA | BB | XX | XX
A1 | B1 | 12 | 34
A2 | B2 | XX | XX
When C3 and C4 = XX, UPDATE C3 = C1 AND C4 = C2
C1 | C2 | C3 | C4
AA | BB | AA | BB
A1 | B1 | 12 | 34
A2 | B2 | A2 | B2