## All we need is an easy explanation of the problem, so here it is.

I struggle to get the result for

here is my dataset

A | B | C | cnt |
---|---|---|---|

2 | 1 | 2 | |

1 | 5 | 5 | |

2 | 1 | 4 | |

1 | 1 | 1 |

result expected

A | B | C | cnt |
---|---|---|---|

2 | 1 | 2 | 2 |

1 | 5 | 5 | 2 |

2 | 1 | 4 | 3 |

1 | 1 | 1 | 1 |

PG 9.5

## How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

### Method 1

**A correlated subquery against a VALUES table should do the trick:**

```
SELECT
t.A, t.B, t.C,
(SELECT COUNT(DISTINCT v.n) FROM (VALUES(t.A),(t.B),(t.C)) AS v(n)) AS cnt
FROM table t
```

If you wanted separate calculations on the values such as both counting and summing, you could use a lateral join (a.k.a `APPLY`

) over `VALUES`

instead:

```
SELECT A, B, C ,D, E, v.countDistinct, v.countNotNull, v.Total
FROM test,
LATERAL (
SELECT COUNT(DISTINCT v.n), COUNT(v.n), SUM(v.n)
FROM (VALUES (A),(B),(C), (D), (E)) AS v(n)
) AS v(countDistinct, countNotNull, Total)
```

### Method 2

You can use nested CASE WHEN structure

`CREATE TABLE test ( "A" INTEGER, "B" INTEGER, "C" INTEGER, "cnt" INTEGER ); INSERT INTO test ("A", "B", "C", "cnt") VALUES ('2', '1', '2', '0'), ('1', '5', '5', '0'), ('2', '1', '4', '0'), ('1', '1', '1', '0');`

`UPDATE test SET cnt = CASE WHEN "A" = "B" THEN CASE WHEN "A" = "C" THEN 1 ELSE 2 END ELSE CASE WHEN "A" = "C" THEN 2 WHEN "B" = "C" THEN 2 ELSE 3 END END`

`SELECT * FROM test`

A | B | C | cnt -: | -: | -: | --: 2 | 1 | 2 | 2 1 | 5 | 5 | 2 2 | 1 | 4 | 3 1 | 1 | 1 | 1

*db<>fiddle here*

**Note: Use and implement method 1 because this method fully tested our system.Thank you 🙂**

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0