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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...
JavaScript hashmap equivalent
...ipt is a high-level language. Its basic primitive (Object) includes a hash table to keep properties. This hash table is usually written in a low-level language for efficiency. Using a simple object with string keys we use an efficiently implemented hash table without any efforts on our part.
How do ...
PostgreSQL query to return results as a comma separated list
Let say you have a SELECT id from table query (the real case is a complex query) that does return you several results.
5 ...
What is “with (nolock)” in SQL Server?
...'t ever rollback transactions, that doesn't matter. And with a insert-only table, the chances of a rollback are slim to none. And if they do occur, you will still fix it all in the end of day variance report.
– Jonathan Allen
Mar 27 '09 at 18:47
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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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How does a Java HashMap handle different objects with the same hash code?
...n, (it might be slightly different from Java 6).
Data structures
Hash table
Hash value is calculated via hash() on key, and it decide which bucket of the hashtable to use for a given key.
Linked list (singly)
When count of elements in a bucket is small, a singly linked list is used.
Red-Black t...
Fast way of counting non-zero bits in positive integer
...se that.
To answer a question in the comments, for bytes I'd use a lookup table. You can generate it at runtime:
counts = bytes(bin(x).count("1") for x in range(256)) # py2: use bytearray
Or just define it literally:
counts = (b'\x00\x01\x01\x02\x01\x02\x02\x03\x01\x02\x02\x03\x02\x03\x03\x04'...
Is there any good dynamic SQL builder library in Java? [closed]
... concept of code generation, where meta classes are generated for database tables and fields. This facilitates a nice, clean DSL but it faces a problem when trying to create queries for databases that are only known at runtime, like in the OP's example above. While jOOQ supports a String based appro...
MySQL: determine which database is selected?
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DUAL is an Oracle table, that was taken over into MySQL. It's a dummy table for operations that do not require an actual table. en.wikipedia.org/wiki/DUAL_table
– Jan Thomä
Nov 11 '11 at 16:03
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What are the disadvantages of using persistent connection in PDO
...tion die when the script terminates abnormally.
If the dead script locked tables, those tables will remain locked until the connection dies or the next script that gets the connection unlocks the tables itself.
If the dead script was in the middle of a transaction, that can block a multitude of ta...