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How to 'insert if not exists' in MySQL?
I started by googling, and found this article which talks about mutex tables.
10 Answers
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SQL Server - SELECT FROM stored procedure
...ure can return multiple result sets, each with its own schema. It's not suitable for using in a SELECT statement.
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Simple Pivot Table to Count Unique Values
This seems like a simple Pivot Table to learn with. I would like to do a count of unique values for a particular value I'm grouping on.
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Add default value of datetime field in SQL Server to a timestamp
I've got a table that collects forms submitted from our website, but for some reason, when they created the table, they didn't put a timestamp in the table. I want it to enter the exact date and time that the record was entered.
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WHERE vs HAVING
... answers on this question didn't hit upon the key point.
Assume we have a table:
CREATE TABLE `table` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`value` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`),
KEY `value` (`value`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
And have 10 rows with both ...
Understanding exactly when a data.table is a reference to (vs a copy of) another data.table
...g a little trouble understanding the pass-by-reference properties of data.table . Some operations seem to 'break' the reference, and I'd like to understand exactly what's happening.
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How to select rows that have current day's timestamp?
I am trying to select only today's records from a database table.
9 Answers
9
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Join between tables in two different databases?
...ccount has appropriate permissions you can use:
SELECT <...>
FROM A.table1 t1 JOIN B.table2 t2 ON t2.column2 = t1.column1;
You just need to prefix the table reference with the name of the database it resides in.
sha...
How to check existence of user-define table type in SQL Server 2008?
I have a user-defined table type. I want to check it's existence before editing in a patch using OBJECT_ID(name, type) function.
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When should I use cross apply over inner join?
...readable and probably less efficient.
Update:
Just checked.
master is a table of about 20,000,000 records with a PRIMARY KEY on id.
This query:
WITH q AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY id) AS rn
FROM master
),
t AS
(
SELEC...