大约有 40,000 项符合查询结果（耗时：0.0259秒） [XML]
Mysql error 1452 - Cannot add or update a child row: a foreign key constraint fails
... have to get rid of those first.
Here's a query that can find those IDs:
SELECT DISTINCT sourcecode_id FROM
sourcecodes_tags tags LEFT JOIN sourcecodes sc ON tags.sourcecode_id=sc.id
WHERE sc.id IS NULL;
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The selected run destination is not valid for this action
...ject icon in the left hand panel. 2) In the right hand panel that appears, select Build Settings » all. 3) You'll see the option to change the SDK. Screenshot: img546.imageshack.us/img546/9808/picture3fh.png
– cwd
Dec 16 '11 at 23:12
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What GRANT USAGE ON SCHEMA exactly do?
...a schema doesn't grant rights on the tables within.
If you have rights to SELECT from a table, but not the right to see it in the schema that contains it then you can't access the table.
The rights tests are done in order:
Do you have `USAGE` on the schema?
No: Reject access.
Yes: Do...
Fast way to discover the row count of a table in PostgreSQL
...in your case.
Instead of getting the exact count (slow with big tables):
SELECT count(*) AS exact_count FROM myschema.mytable;
You get a close estimate like this (extremely fast):
SELECT reltuples::bigint AS estimate FROM pg_class where relname='mytable';
How close the estimate is depends on ...
SQL JOIN vs IN performance?
...king, IN and JOIN are different queries that can yield different results.
SELECT a.*
FROM a
JOIN b
ON a.col = b.col
is not the same as
SELECT a.*
FROM a
WHERE col IN
(
SELECT col
FROM b
)
, unless b.col is unique.
However, this is the syno...
How do you do a limit query in JPQL or HQL?
...
// SQL: SELECT * FROM table LIMIT start, maxRows;
Query q = session.createQuery("FROM table");
q.setFirstResult(start);
q.setMaxResults(maxRows);
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IntelliJ: Working on multiple projects
...ven Projects" window (View > Tool Windows > Maven Projects) and then select the additional pom file you want to import.
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MySQL get row position in ORDER BY
...
Use this:
SELECT x.id,
x.position,
x.name
FROM (SELECT t.id,
t.name,
@rownum := @rownum + 1 AS position
FROM TABLE t
JOIN (SELECT @rownum := 0) r
ORDER BY t.name)...
MySQL Conditional Insert
...
If your DBMS does not impose limitations on which table you select from when you execute an insert, try:
INSERT INTO x_table(instance, user, item)
SELECT 919191, 123, 456
FROM dual
WHERE NOT EXISTS (SELECT * FROM x_table
WHERE user = ...
How to split a comma-separated value to columns
...TRING(@string, @pos, @len)
INSERT INTO @out_put ([value])
SELECT LTRIM(RTRIM(@value)) AS [column]
SET @pos = CHARINDEX(@delimiter, @string, @pos + @len) + 1
END
RETURN
END
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