Re: [sqlite] updating records in table A from joined records in table B
@Pavel: close. @David: that works. = DROP TABLE IF EXISTS `table_a`; CREATE TABLE `table_a` (`key` int(11), `value` float, `str` varchar(255)); DROP TABLE IF EXISTS `table_b`; CREATE TABLE `table_b` (`key` int(11), `value` float, `str` varchar(255)); INSERT INTO `table_a` (`key`, `value`, `str`) VALUES (1, 1.0, 'mon'); INSERT INTO `table_a` (`key`, `value`, `str`) VALUES (2, 2.0, 'tue'); INSERT INTO `table_a` (`key`, `value`, `str`) VALUES (3, 3.0, 'wed'); INSERT INTO `table_b` (`key`, `value`, `str`) VALUES (1, 101.0, 'mon'); INSERT INTO `table_b` (`key`, `value`, `str`) VALUES (2, 102.0, 'may'); INSERT INTO `table_b` (`key`, `value`, `str`) VALUES (4, 104.0, 'jun'); SELECT 'BEFORE UPDATE'; SELECT * FROM `table_a` ORDER BY `key`; UPDATE table_a SET value = (SELECT table_b.value FROM table_b WHERE table_a.key=table_b.key) WHERE EXISTS (SELECT 1 FROM table_b WHERE table_a.key=table_b.key); SELECT 'AFTER UPDATE'; SELECT * FROM `table_a` ORDER BY `key`; = results in = sqlite> .read sqlite_update_test.sql BEFORE UPDATE 1|1.0|mon 2|2.0|tue 3|3.0|wed AFTER UPDATE 1|101.0|mon 2|102.0|tue 3|3.0|wed = The WHERE EXISTS condition is required to prevent updating rows where there is NOT a match. Pavel's suggestion (which was identical except for the WHERE EXISTS clause) would set table_a.value fields to NULL on rows where there wasn't a match. So I see why David says it's a "little redundant": both sub-queries contain 'FROM table_b WHERE table_a.key=table_b.key'. But it works. Thanks. ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] updating records in table A from joined records in table B
> ... that is to say, update table_a.value from table_b.value, but only
> on rows where table_a.key = table_b.key
update table_a set value =
(select table_b.value from table_b where table_b.key = table_a.key)
Pavel
On Fri, Apr 1, 2011 at 8:42 PM, Robert Poor wrote:
> I'd like to be able to update specific records in table A from joined
> records in table B. So for example:
>
> CREATE TABLE "table_a" ("key" integer, "value" float);
> CREATE TABLE "table_b" ("key" integer, "value" float);
> INSERT INTO "table_a" ("key", "value") VALUES (1, 1.0), (2, 2.0),(3,
> 3.0);
> INSERT INTO "table_b" ("key", "value") VALUES (1, 101.0), (2, 102.0),(4,
> 104.0);
>
> In an imaginary version of SQLite ;) this might be written as:
>
> # UPDATE table_a
> # JOIN table_b
> # SET table_a.value = table_b.value
> # WHERE table_a.key1 = table_b.key
>
> resulting in table_a:
>
> key | value
> 1 | 101
> 2 | 102
> 3 | 3
>
> ... that is to say, update table_a.value from table_b.value, but only
> on rows where table_a.key = table_b.key
>
> I've pored over the UPDATE syntax, but I don't see a way to do this.
> What's the idiom in SQLite?
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> sqlite-users@sqlite.org
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>
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Re: [sqlite] updating records in table A from joined records in table B
A bit redundant, but how about:
CREATE TABLE table_a (akey integer, avalue float);
CREATE TABLE table_b (bkey integer, bvalue float);
INSERT INTO table_a (akey, avalue) VALUES (1, 1.0);
INSERT INTO table_a (akey, avalue) VALUES (2, 2.0);
INSERT INTO table_a (akey, avalue) VALUES (3, 3.0);
INSERT INTO table_b (bkey, bvalue) VALUES (1, 101.0);
INSERT INTO table_b (bkey, bvalue) VALUES (2, 102.0);
INSERT INTO table_b (bkey, bvalue) VALUES (4, 104.0);
UPDATE table_a SET avalue=(SELECT bvalue FROM table_b WHERE akey=bkey)
WHERE EXISTS(SELECT 1 FROM table_b WHERE akey=bkey);
I think there is no multi-table update idiom in SQLite because there
isn't one in SQL.
--David
Robert Poor writes:
> I'd like to be able to update specific records in table A from joined
> records in table B. So for example:
>
> CREATE TABLE "table_a" ("key" integer, "value" float);
> CREATE TABLE "table_b" ("key" integer, "value" float);
> INSERT INTO "table_a" ("key", "value") VALUES (1, 1.0), (2, 2.0),(3,
> 3.0);
> INSERT INTO "table_b" ("key", "value") VALUES (1, 101.0), (2, 102.0),(4,
> 104.0);
>
> In an imaginary version of SQLite ;) this might be written as:
>
> # UPDATE table_a
> # JOIN table_b
> #SET table_a.value = table_b.value
> # WHERE table_a.key1 = table_b.key
>
> resulting in table_a:
>
> key | value
> 1 | 101
> 2 | 102
> 3 | 3
>
> ... that is to say, update table_a.value from table_b.value, but only
> on rows where table_a.key = table_b.key
>
> I've pored over the UPDATE syntax, but I don't see a way to do this.
> What's the idiom in SQLite?
> ___
> sqlite-users mailing list
> sqlite-users@sqlite.org
> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
___
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[sqlite] updating records in table A from joined records in table B
I'd like to be able to update specific records in table A from joined
records in table B. So for example:
CREATE TABLE "table_a" ("key" integer, "value" float);
CREATE TABLE "table_b" ("key" integer, "value" float);
INSERT INTO "table_a" ("key", "value") VALUES (1, 1.0), (2, 2.0),(3, 3.0);
INSERT INTO "table_b" ("key", "value") VALUES (1, 101.0), (2, 102.0),(4, 104.0);
In an imaginary version of SQLite ;) this might be written as:
# UPDATE table_a
# JOIN table_b
#SET table_a.value = table_b.value
# WHERE table_a.key1 = table_b.key
resulting in table_a:
key | value
1 | 101
2 | 102
3 | 3
... that is to say, update table_a.value from table_b.value, but only
on rows where table_a.key = table_b.key
I've pored over the UPDATE syntax, but I don't see a way to do this.
What's the idiom in SQLite?
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