sqlite3 group by
I have 2 tables fun (master) and blk (slave).
sqlite> select * from fun;
id mod_id name freq
---------- ---------- ----------- ----------
1 1 adpcm_coder 99108
2 1 adpcm_decod 0
I want to count how many blk's there are for fun, so I use "group by":
sqlite> SELECT fun.*, count(blk.id) as no_blk FROM fun, blk WHERE fun.id=blk.fun_id GROUP BY (blk.fun_id);
id mod_id name freq no_blk
---------- 开发者_JAVA百科 ---------- ----------- ---------- ----------
1 1 adpcm_coder 99108 12
The 2nd row is rejected since blks for it do not exists. Howto get result like this?
id mod_id name freq no_blk
---------- ---------- ----------- ---------- ----------
1 1 adpcm_coder 99108 12
2 1 adpcm_decod 0 0
You want an OUTER JOIN
.
Also you should GROUP BY
all non-aggregated columns in your SELECT
clause.
Try something like this:
SELECT fun.id, fun.mod_id, fun.name, fun.freq, count(blk.id) as no_blk
FROM fun
LEFT OUTER JOIN blk
ON blk.fun_id = fun.id
GROUP BY fun.id, fun.mod_id, fun.name, fun.freq;
Adam is correct; another approach:
SELECT fun.*, count(blk.id) as no_blk FROM fun, blk
WHERE fun.id=blk.fun_id GROUP BY (blk.fun_id)
UNION
SELECT fun.*, 0 as no_blk FROM fun, blk
WHERE fun.id not in (SELECT fun.id from fun, blk WHERE fun.id=blk.fun_id);
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