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selecting unique values from a column
I have a MySQL table which contains the following type of information:
9 Answers
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What is the fastest/most efficient way to find the highest set bit (msb) in an integer in C?
...h gives 31-lzcnt for non-zero inputs.)
There's unfortunately no way to portably take advantage of the various CLZ instructions on non-x86 platforms that do define the result for input=0 as 32 or 64 (according to the operand width). x86's lzcnt does that, too, while bsr produces a bit-index that th...
How to choose the id generation strategy when using JPA and Hibernate
...that are unique only when no other process is inserting data into the same table. Do not use in a cluster.
identity
supports identity columns in DB2, MySQL, MS SQL Server, Sybase and HypersonicSQL. The returned identifier is of type long, short or int.
sequence
uses a sequence in DB2, PostgreSQL, Or...
Are GUID collisions possible?
...ither unique (for things like version 1 GUIDs), or both unique and unpredictable (for things like version 4 GUIDs). SQL Server's implementation for their NEWID() function appears to use a 128-bit random number, so you're not going to get a collision.
For a 1% chance of collision, you'd need to gen...
How to export and import a .sql file from command line with options? [duplicate]
...an we set constraints like enable/disable foreign key check or export only table structure with mysqldump
– AZinkey
Feb 28 '15 at 2:48
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differentiate null=True, blank=True in django
...e)
The database fields created for PostgreSQL 9.4 are :
CREATE TABLE Test (
id serial NOT NULL,
"charNull" character varying(10),
"charBlank" character varying(10) NOT NULL,
"charNullBlank" character varying(10),
"intNull" in...
How can I select multiple columns from a subquery (in SQL Server) that should have one record (selec
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select t1.*, sq.*
from table1 t1,
(select a,b,c from table2 ...) sq
where ...
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Export and Import all MySQL databases at one time
...-databases > alldb.sql
mysqldump -u root -p --all-databases --skip-lock-tables > alldb.sql
Import:
mysql -u root -p < alldb.sql
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fol...
Delete/Reset all entries in Core Data?
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You can delete the SQLite file - but I choose to do it by purging the tables individually with a functions:
- (void) deleteAllObjects: (NSString *) entityDescription {
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription enti...
Can we omit parentheses when creating an object using the “new” operator?
...nt precedence. According to MDN the part of JavaScript operator precedence table we are interested in looks like:
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