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MySQL - UPDATE query based on SELECT Query
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You can actually do this one of two ways:
MySQL update join syntax:
UPDATE tableA a
INNER JOIN tableB b ON a.name_a = b.name_b
SET validation_check = if(start_dts > end_dts, 'VALID', '')
-- where clause can go here
ANSI SQL syntax:
UPDATE tableA SET validation_c...
MYSQL Truncated incorrect DOUBLE value
When the SQL query below is executed:
10 Answers
10
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Unable to cast object of type 'System.DBNull' to type 'System.String`
...ed to check against normal "null" value. The DBNull.Value would work for a SqlDataReader or a SqlParameter - but not for this object here.
– marc_s
May 15 '09 at 20:27
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How do I kill all the processes in Mysql “show processlist”?
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You need to kill them one by one, MySQL does not have any massive kill command. You can script it in any language, for example in PHP you can use something like:
$result = mysql_query("SHOW FULL PROCESSLIST");
while ($row=mysql_fetch_array($result)) {
$proce...
What's faster, SELECT DISTINCT or GROUP BY in MySQL?
...esn't have to sort the output, and GROUP BY by default does. However, in MySQL even a DISTINCT+ORDER BY might still be faster than a GROUP BY due to the extra hints for the optimizer as explained by SquareCog.
– rustyx
Jan 25 '15 at 15:03
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Efficiently updating database using SQLAlchemy ORM
...m starting a new application and looking at using an ORM -- in particular, SQLAlchemy.
6 Answers
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How to group time by hour or by 10 minutes
...uncated at the level you specify.
'2000' is an "anchor date" around which SQL will perform the date math. Jereonh discovered below that you encounter an integer overflow with the previous anchor (0) when you group recent dates by seconds or milliseconds.†
SELECT DATEADD(MINUTE, DATEDIFF(MIN...
Tools for Generating Mock Data? [closed]
...le (for "Populate database" option). Moreover going for one of the demos (hsqldb) with maven results in errors as well. To me it seems like the tool not in a good shape, thus not worth loosing the time with it.
– Peter Butkovic
Nov 7 '13 at 9:11
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How to use count and group by at the same select statement
I have an sql select query that has a group by.
I want to count all the records after the group by statement.
Is there a way for this directly from sql?
For example, having a table with users I want to select the different towns and the total number of users
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Problem with converting int to string in Linq to entities
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With EF v4 you can use SqlFunctions.StringConvert. There is no overload for int so you need to cast to a double or a decimal. Your code ends up looking like this:
var items = from c in contacts
select new ListItem
{
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