common table expression - SQLite Concatenating Column values -

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there similar answers other database types haven't found example sqlite, i've included answer came with.

the problem

given table following

╔══════════╦══════╗ ║ item     ║ tag  ║ ╠══════════╬══════╣ ║ "item1"  ║ "a"  ║ ║ "item1"  ║ "b"  ║ ║ "item1"  ║ "c"  ║ ║ "item2"  ║ "a"  ║ ║ "item1"  ║ "d"  ║ ║ "item2"  ║ "f"  ║ ║ "item1"  ║ "e"  ║ ╚══════════╩══════╝

create output of:

╔═══════════╦═════════════╗ ║  item     ║    tags     ║ ╠═══════════╬═════════════╣ ║  "item1"  ║ "a,b,c,d,e" ║ ║  "item2"  ║ "a,f"       ║ ╚═══════════╩═════════════╝

that's group_concat() for:

select item,        group_concat(tag) tags (select item, tag       t       order item, tag) group item;

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