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Efficient Algorithm for Bit Reversal (from MSB->LSB to LSB->MSB) in C
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NOTE: All algorithms below are in C, but should be portable to your language of choice (just don't look at me when they're not as fast :)
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Low Memory (32-bit int, 32-bit machine)(from here):
unsigned int
reverse(register unsigned int x)
{
x = (((x & 0xaaaaaaaa)...
INSERT IF NOT EXISTS ELSE UPDATE?
...ot in the insert list will be set to NULL if the row already exists in the table. This is why there's a subselect for the ID column: In the replacement case the statement would set it to NULL and then a fresh ID would be allocated.
This approach can also be used if you want to leave particular fiel...
Create boolean column in MySQL with false as default value?
I want to create a table in MySQL with a boolean column whose default value is false . But it's accepting NULL as default...
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How do I handle too long index names in a Ruby on Rails ActiveRecord migration?
...an unique index that gets created from the foreign keys of four associated tables:
9 Answers
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SQL Server indexes - ascending or descending, what difference does it make?
...rily matters when used with composite indexes:
CREATE INDEX ix_index ON mytable (col1, col2 DESC);
can be used for either:
SELECT *
FROM mytable
ORDER BY
col1, col2 DESC
or:
SELECT *
FROM mytable
ORDER BY
col1 DESC, col2
, but not for:
SELECT *
FROM mytable
ORDE...
MySQL Like multiple values
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Why not you try REGEXP. Try it like this:
SELECT * FROM table WHERE interests REGEXP 'sports|pub'
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TSQL Pivot without aggregate function
I have a table like this...
9 Answers
9
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How to get ID of the last updated row in MySQL?
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I've found an answer to this problem :)
SET @update_id := 0;
UPDATE some_table SET column_name = 'value', id = (SELECT @update_id := id)
WHERE some_other_column = 'blah' LIMIT 1;
SELECT @update_id;
EDIT by aefxx
This technique can be further expanded to retrieve the ID of every row affected by...
Get the last inserted row ID (with SQL statement) [duplicate]
I want to get the new created ID when you insert a new record in table.
3 Answers
3
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Change MySQL default character set to UTF-8 in my.cnf?
...y.cnf settings worked for me as well. Additionally, I had to make sure the table was set properly, such as ALTER TABLE Table CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
– Chris Livdahl
May 26 '11 at 19:26
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