大约有 9,859 项符合查询结果（耗时：0.0140秒） [XML]
Fastest check if row exists in PostgreSQL
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Use the EXISTS key word for TRUE / FALSE return:
select exists(select 1 from contact where id=12)
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MySQL “WITH” clause
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You might be interested in somethinkg like this:
select * from (
select * from table
) as Subquery
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How can I convert comma separated string into a List
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Here is one way of doing it:
List<int> TagIds = tags.Split(',').Select(int.Parse).ToList();
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What's faster, SELECT DISTINCT or GROUP BY in MySQL?
...'t, then use DISTINCT.
GROUP BY in MySQL sorts results. You can even do:
SELECT u.profession FROM users u GROUP BY u.profession DESC
and get your professions sorted in DESC order.
DISTINCT creates a temporary table and uses it for storing duplicates. GROUP BY does the same, but sortes the disti...
What is the difference between “INNER JOIN” and “OUTER JOIN”?
...he intersection of the two tables, i.e. the two rows they have in common.
select * from a INNER JOIN b on a.a = b.b;
select a.*, b.* from a,b where a.a = b.b;
a | b
--+--
3 | 3
4 | 4
Left outer join
A left outer join will give all rows in A, plus any common rows in B.
select * from a LEFT OUT...
How can I select every other line with multiple cursors in Sublime Text?
In Sublime Text 2, is it possible to instantly select every other (or odd/even) line and place multiple cursors on those lines?
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List all sequences in a Postgres db 8.1 with SQL
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The following query gives names of all sequences.
SELECT c.relname FROM pg_class c WHERE c.relkind = 'S';
Typically a sequence is named as ${table}_id_seq. Simple regex pattern matching will give you the table name.
To get last value of a sequence use the following query:...
How to Display Selected Item in Bootstrap Button Dropdown Title
...ied ur sample link but it is not working there, besides I need to grab the selected value as well to post to database later
– Suffii
Nov 18 '12 at 4:57
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How can I disable the UITableView selection?
When you tap a row in a UITableView , the row is highlighted and selected. Is it possible to disable this so tapping a row does nothing?
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ROW_NUMBER() in MySQL
...asy, but actually it kind of isn't).
I often plump for a null-self-join:
SELECT t0.col3
FROM table AS t0
LEFT JOIN table AS t1 ON t0.col1=t1.col1 AND t0.col2=t1.col2 AND t1.col3>t0.col3
WHERE t1.col1 IS NULL;
“Get the rows in the table for which no other row with matching col1,col2 has a hi...