Question

I’m having trouble doing the following in SQL with Postgres. My program has an ordered set of numbers. In my database I have the table which stores all numbers in rows with extra data. These rows are also placed in order.

For example my set I need to find is;

1,5,6,1,3

The database has rows

row1 4
row2 5
row3 1
row4 5
row5 6
row6 1
row7 3
row8 2
row9 7

In the example above it’s easy to see that my set is found from row 3 to to row7. Still doing such in SQL is a mystery to me. I’m reading some articles regarding pivot tables, still I’m hoping there’s an easier way.

Answer 1

Both data-sets need to have fields that identify the order.

And provided that the ordering column is a sequential consecutive set of numbers, then this is possible, although I doubt it’s very quick.

Table 1                 Table 2

id | value              id | value
 1    4                  1    1
 2    5                  2    5
 3    1                  3    6
 4    5                  4    1
 5    6                  5    3
 6    1                  
 7    3                  
 8    2                  
 9    7                  

Then this query…

SELECT
  *
FROM
  table_1
INNER JOIN
  (
    SELECT
      MIN(table_1.id)    AS first_id,
      MAX(table_1.id)    AS last_id
    FROM
      table_1
    INNER JOIN
      table_2
        ON table_1.value = table_2.value
    GROUP BY
      table_1.id - table_2.id
    HAVING
      COUNT(*) = (SELECT COUNT(*) FROM table_2)
  )
  AS matched_sets
    ON  matched_sets.first <= table_1.id
    AND matched_sets.last  >= table_1.id