大约有 300 项符合查询结果（耗时：0.0253秒） [XML]
MySQL select 10 random rows from 600K rows fast
...e query that has excellent performance and works with gaps:
SELECT * FROM tbl AS t1 JOIN (SELECT id FROM tbl ORDER BY RAND() LIMIT 10) as t2 ON t1.id=t2.id
This query on a 200K table takes 0.08s and the normal version (SELECT * FROM tbl ORDER BY RAND() LIMIT 10) takes 0.35s on my machine.
This ...
How to write a foreach in SQL Server?
...n in the hints.
This is the proc code:
CREATE PROC [dbo].[PRC_FOREACH] (@TBL VARCHAR(100) = NULL, @EXECUTE NVARCHAR(MAX)=NULL, @DB VARCHAR(100) = NULL) AS BEGIN
--LOOP BETWEEN EACH TABLE LINE
IF @TBL + @EXECUTE IS NULL BEGIN
PRINT '@TBL: A TABLE TO MAKE OUT EACH LINE'
PRI...
Maximum Java heap size of a 32-bit JVM on a 64-bit OS
... a code example, and details covering all OSes.
– TGP1994
Jun 17 '13 at 21:42
3
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SQLite: How do I save the result of a query as a CSV file?
...
sqlite> .mode csv
sqlite> .output test.csv
sqlite> select * from tbl1;
sqlite> .output stdout
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DropDownList's SelectedIndexChanged event not firing
... have fixed it, thank you. Can you explain why?
– TGP1994
Feb 5 '11 at 15:05
2
@TGP1994 :The Auto...
Skip certain tables with mysqldump
...
for multiple databases:
mysqldump -u user -p --ignore-table=db1.tbl1 --ignore-table=db2.tbl1 --databases db1 db2 ..
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Computed / calculated / virtual / derived columns in PostgreSQL
...ed columns are introduced with Postgres 12. Trivial example:
CREATE TABLE tbl (
int1 int
, int2 int
, product bigint GENERATED ALWAYS AS (int1 * int2) STORED
);
db<>fiddle here
VIRTUAL generated columns may come with one of the next iterations. (Not in Postgres 13, yet) .
Relate...
-didSelectRowAtIndexPath: not being called
... [self.view addGestureRecognizer:tap];
– coolcool1994
Jul 4 '13 at 21:31
28
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Simultaneously merge multiple data.frames in a list
...matchname party st district chamber senate1993 name.x v2.x v3.x v4.x senate1994 name.y
#1 ALGIERE 200 RI 026 S NA <NA> NA NA NA NA <NA>
#2 ALVES 100 RI 019 S NA <NA> NA NA NA NA <NA>
#3 BAD...
PostgreSQL: Modify OWNER on all tables simultaneously in PostgreSQL
...you likely want views and sequences too. Here's what I did:
Tables:
for tbl in `psql -qAt -c "select tablename from pg_tables where schemaname = 'public';" YOUR_DB` ; do psql -c "alter table \"$tbl\" owner to NEW_OWNER" YOUR_DB ; done
Sequences:
for tbl in `psql -qAt -c "select sequence_name ...