for each in sql?

Question

How can I write the following query in SQL? I have a table where column B has erroneously been filled with duplicate values. The easiest way to find these duplicates is by comparing to another column A in the same table which should generally be a 1-to-1 correspondence, the table will possibly contain multiple rows of the repeated column B value

Something like this

column A | column B
-------------------
00234211 | T 156   
00011331 | T 157   
00011331 | T 157   
04600100 | T 157  <--- This is probably an erroneous value, show me every row for "T 157"
07740010 | T 159

How would I write a SQL query resembling this terrible pseudo code

  for all rows:
    let A = columnA_value, B = columnB_value
    for rows where columnA = A:
      IF COUNT(columnB) > 1, 
          SHOW all rows WHERE columnA = A

Possible duplicate of [Find duplicate records in MySQL](https://stackoverflow.com/questions/854128/find-duplicate-records-in-mysql) — dfundako, Mar 27 '18 at 19:24
SQL is a set based language. Why would you need double for loop in SQL????? — Eric, Mar 27 '18 at 19:48

score 1 · Accepted Answer · answered Mar 27 '18 at 19:25

1

Hmmm. I think you want:

select t.*
from t
where exists (select 1 from t t2 where t2.b = t.b and t2.a <> t.a);

answered Mar 27 '18 at 19:25

Gordon Linoff

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for each in sql?

1 Answers1