SELECT COUNT(*) as sum FROM data WHERE aa < 100 LIMIT 1;
sum
--------
1160
(1 row)
我预期结果为1或0,但结果为1160
原因:
- Postgres读取所有行 FROM data WHERE aa < 100
- Postgres然后将count(*)它们
- Postgres然后LIMIT是 count
SELECT COUNT(*) as sum FROM data WHERE aa < 100 LIMIT 1;
sum
--------
1160
(1 row)
我预期结果为1或0,但结果为1160
原因: