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How to 'insert if not exists' in MySQL?
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Solution:
INSERT INTO `table` (`value1`, `value2`)
SELECT 'stuff for value1', 'stuff for value2' FROM DUAL
WHERE NOT EXISTS (SELECT * FROM `table`
WHERE `value1`='stuff for value1' AND `value2`='stuff for value2' LIMIT 1)
Explanation:
The innermost query
SELECT *...
How to find a text inside SQL Server procedures / triggers?
... find text....
DECLARE @Search varchar(255)
SET @Search='[10.10.100.50]'
SELECT DISTINCT
o.name AS Object_Name,o.type_desc
FROM sys.sql_modules m
INNER JOIN sys.objects o ON m.object_id=o.object_id
WHERE m.definition Like '%'+@Search+'%'
ORDER BY 2,1
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How to define “type disjunction” (union types)?
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Miles Sabin describes a very nice way to get union type in his recent blog post Unboxed union types in Scala via the Curry-Howard isomorphism:
He first defines negation of types as
type ¬[A] = A => Nothing
using De Morgan's law this allows him to define union ty...
Mysql: Select rows from a table that are not in another
How to select all rows in one table that do not appear on another?
8 Answers
8
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ERROR 1396 (HY000): Operation CREATE USER failed for 'jack'@'localhost'
...seem to be unable to re-create a simple user I've deleted, even as root in MySQL.
24 Answers
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Intersection and union of ArrayLists in Java
... Test().intersection(list1, list2));
System.out.println(new Test().union(list1, list2));
}
public <T> List<T> union(List<T> list1, List<T> list2) {
Set<T> set = new HashSet<T>();
set.addAll(list1);
set.addAll(list2);
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How do I check if a column is empty or null in MySQL?
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This will select all rows where some_col is NULL or '' (empty string)
SELECT * FROM table WHERE some_col IS NULL OR some_col = '';
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SELECT INTO Variable in MySQL DECLARE causes syntax error?
I´d like to SELECT a single value into a variable. I´d tried to following:
11 Answers
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Select all columns except one in MySQL?
I'm trying to use a select statement to get all of the columns from a certain MySQL table except one. Is there a simple way to do this?
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MySQL maximum memory usage
...e to know how it is possible to set an upper limit on the amount of memory MySQL uses on a Linux server.
6 Answers
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