1

Using PostgreSQL 9.6, I'm trying to insert rows into a table map, generated from another table tbl.

tbl

name in1 in2
a 1
b 2 {3}
c 4 {5,6}
d 7 {8,9,10}

Should result in this:

map

name out1 out2
a 1 1
b 2 2
b 2 3
c 4 4
c 4 5
c 4 6
d 7 7
d 7 8
d 7 9
d 7 10

in1 and each value in the array in2 should get entries for user name. I can't figure out how best to iterate through the array, whether it's a subselect, or a built-in operator.

So far I have:

INSERT INTO map(name, out1, out2)
SELECT (name, in1, in1)
FROM
    tbl;

UPDATE map
SET out2 = 
    (loop possibly of in2?)
FROM
    tbl t
WHERE
     name = t.name;
Erwin Brandstetter
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Daniel Powley
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3 Answers3

0
insert into map (name, out1, out2)
select * from (
select name, int1, unnest(int2) int2 from tbl
union all
select name, int1, int1 from tbl) x
mcg1103
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0

Not sure which format your array is stored, but here's one method that works if it's a TEXT column. Using the split-to-table function combined with replace, then casting that to integer.

select *
from (
    select pname, in1 as out1, in1 as out2
    from tbl
    union
    select pname, in1 as out1,  
    nullif(regexp_replace(regexp_split_to_table(in2, ','), '\D', '','g'), '')::integer
    from tbl
  )z
where out2 is not null
order by 1,2

Output:

pname out1 out2
a 1 1
b 2 2
b 2 3
c 4 4
c 4 5
c 4 6
d 7 7
d 7 8
d 7 9
d 7 10

Fiddle found here. Just wrap with an update statement.

Isolated
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0

Simply:

INSERT INTO map (name, out1, out2)
SELECT pname, in1, unnest(in1 || in2)
FROM   tbl

Assuming this table definition:

CREATE TABLE tbl (
  pname text PRIMARY KEY
, in1   integer NOT NULL
, in2   integer[]  --  can be NULL?
);

fiddle

Notably, in2 is an integer array (integer[]). Else, cast with in2::int[] - you have valid array literals on display.

About the element-to-array concatenation in in1 || in2, see:

in1 and in2 can be NULL, but consider corner cases demonstrated in my fiddle. You may want to move unnest() to a LATERAL subquery to steer corner cases. See:

Careful with multiple set-returning functions like unnest() in the SELECT list, especially before Postgres 10. (Not an issue with just one.) See:

Erwin Brandstetter
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  • should have mentioned in1 is int NOT NULL, and in2 is int[] (can be NULL). Returning an error that in1 is of type integer but expression is of type character varying (name of of type varchar, for the record) – Daniel Powley Sep 07 '22 at 19:56
  • @DanielPowley: *"`in1` is `int NOT NULL`, and `in2` is `int[]`"* - then there is no `varchar` involved, and the error makes no sense. Should just work, as demonstrated in the fiddle (in pg 15 and pg 9.6 alike). – Erwin Brandstetter Sep 07 '22 at 20:00
  • Tried again. This worked, looks like my ordering was wrong – Daniel Powley Sep 07 '22 at 22:25