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Unique constraint that allows empty values in MySQL
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Yes, you can do this. See the MySQL reference (version 5.5).
A UNIQUE index creates a constraint such that all values in the index must be distinct. An error occurs if you try to add a new row with a key value that matches an existing row. For all eng...
Equals(=) vs. LIKE
... operators produce obviously different results. Allow me to quote from the MySQL manual:
Per the SQL standard, LIKE performs matching on a per-character basis, thus it can produce results different from the = comparison operator:
mysql> SELECT 'ä' LIKE 'ae' COLLATE latin1_german2_ci;
+----...
MySQL/SQL: Group by date only on a Datetime column
...son. I would expect it to fail anywhere else as well. Can you confirm that MySQL actually handles this query?
– Tomalak
Dec 14 '08 at 15:56
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MySQL convert date string to Unix timestamp
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You will certainly have to use both STR_TO_DATE to convert your date to a MySQL standard date format, and UNIX_TIMESTAMP to get the timestamp from it.
Given the format of your date, something like
UNIX_TIMESTAMP(STR_TO_DATE(Sales.SalesDate, '%M %e %Y %h:%i%p'))
Will gives you a valid timestam...
How to select the last record of a table in SQL?
...s something like
Sql Server
SELECT TOP 1 * FROM Table ORDER BY ID DESC
MySql
SELECT * FROM Table ORDER BY ID DESC LIMIT 1
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SQL: deleting tables with prefix
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You cannot do it with just a single MySQL command, however you can use MySQL to construct the statement for you:
In the MySQL shell or through PHPMyAdmin, use the following query
SELECT CONCAT( 'DROP TABLE ', GROUP_CONCAT(table_name) , ';' )
AS statement...
Duplicating a MySQL table, indices, and data
How do I copy or clone or duplicate the data, structure,
and indices of a MySQL table to a new one?
10 Answers
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How to convert timestamp to datetime in MySQL?
How to convert 1300464000 to 2011-03-18 16:00:00 in MySQL?
5 Answers
5
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Two single-column indexes vs one two-column index in MySQL?
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"MySQL can use multiple-column indexes for queries that test all the columns in the index, or queries that test just the first column, the first two columns, the first three columns, and so on. If you specify the columns in th...
Illegal mix of collations MySQL Error
...E your_table_name CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
MySQL sneaks swedish in there sometimes for no sensible reason.
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