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When should I use a composite index?
...nefit a query that uses those fields for joining, filtering, and sometimes selecting. It will also benefit queries that use left-most subsets of columns in that composite. So the above index will also satisfy queries that need
index( column_A, column_B, column_C )
index( column_A, column_B )
index(...
What is the best way to insert source code examples into a Microsoft Word document?
... it may be too small ...
... so you may have to change its size
Having selected the text box, right-click on it, then choose Insert Caption ...
In the Caption menu, if you don't have one already, click New Label, and set the new label to "Code", click OK ...
... then in the Caption dialog, s...
How to get duplicate items from a list using LINQ? [duplicate]
...
var duplicates = lst.GroupBy(s => s)
.SelectMany(grp => grp.Skip(1));
Note that this will return all duplicates, so if you only want to know which items are duplicated in the source list, you could apply Distinct to the resulting sequence or use the solution...
How do you perform a left outer join using linq extension methods
...=> bar.Foo_Id,
(x,y) => new { Foo = x, Bars = y })
.SelectMany(
x => x.Bars.DefaultIfEmpty(),
(x,y) => new { Foo=x.Foo, Bar=y});
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MYSQL OR vs IN performance
...for future Googlers. Total count of returned results is 7264 out of 10000
SELECT * FROM item WHERE id = 1 OR id = 2 ... id = 10000
This query took 0.1239 seconds
SELECT * FROM item WHERE id IN (1,2,3,...10000)
This query took 0.0433 seconds
IN is 3 times faster than OR
...
How to select multiple files with ?
How to select multiple files with <input type="file"> ?
9 Answers
9
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Get PostGIS version
...s like GEOS and proj4 you might want to get their versions too. Then use:
SELECT PostGIS_full_version();
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MySQL一次主从数据不一致的问题解决过程 - 数据库(内核) - 清泛网 - 专注C/...
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pt-table-checksum校验数据一致性。
从库mysql操作
GRANT SELECT,PROCESS, SUPER, REPLICATION SLAVE ON *.* TO 'checksums'@'192.168.1.100' IDENTIFIED BY 'slavecheck'; flush privileges;
主库mysql操作
GRANT SELECT, PROCESS, SUPER, REPLICATION SLAVE ON *.* TO 'checksums'@'19...
How to convert float to varchar in SQL Server
...
Try using the STR() function.
SELECT STR(float_field, 25, 5)
STR() Function
Another note: this pads on the left with spaces. If this is a problem combine with LTRIM:
SELECT LTRIM(STR(float_field, 25, 5))
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disable all form elements inside div
...
Try using the :input selector, along with a parent selector:
$("#parent-selector :input").attr("disabled", true);
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