I have table
| Column A | Column B | Column C |
|---|---|---|
| 1 | a | d |
| 2 | b | e |
| 3 | c | f |
and very large .csv file (about 1M rows). It contains Columns A, B and C.
| Column A | Column B | Column C |
|---|---|---|
| 4 | a | d |
| 5 | b | w |
| 6 | c | f |
I need to extract rows from table where (B = 'a' and C = 'd') or (B = 'b' and C = 'w') or (B = 'c' and C = 'f')
Result will be:
| Column A | Column B | Column C |
|---|---|---|
| 1 | a | d |
| 3 | c | f |
I've tried query like in description, but it's too large for request (1M rows)
CodePudding user response：
You are basically trying to join on the columns (b, c) manually. However, SQL knows how to do a join more efficiently.
Import the CSV file as a temporary table, analyze it, create a multi-column index on its (b, c), then do a join like this:
SELECT R.*
FROM realTable R
JOIN csvTable C
ON R.b = C.b AND R.c = C.c;