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How do MySQL indexes work?
...be faster to go through the pages one by one (in a database, this is "poor selectivity").
For a 10-page book, it makes no sense to make an index, as you may end up with a 10-page book prefixed by a 5-page index, which is just silly - just scan the 10 pages and be done with it.
The index also needs t...
String concatenation in MySQL
...most DBMSs use of + or || for concatenation. It uses the CONCAT function:
SELECT CONCAT(first_name, " ", last_name) AS Name FROM test.student
As @eggyal pointed out in comments, you can enable string concatenation with the || operator in MySQL by setting the PIPES_AS_CONCAT SQL mode.
...
Why there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT clause?
...pdated) values(null, null);
Query OK, 1 row affected (0.06 sec)
mysql> select * from t5;
+----+---------------------+---------------------+
| id | stamp_created | stamp_updated |
+----+---------------------+---------------------+
| 2 | 2009-04-30 09:44:35 | 2009-04-30 09:44:35 |
+...
IntelliJ IDEA way of editing multiple lines
...ossibility to edit multiple lines.
Use:
Alt + Shift + Mouse click
for selection. More about this new improvement in IntelliJ blogpost here. Very useful feature.
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How to add column if not exists on PostgreSQL?
...s, _col text, _type regtype)
RETURNS bool AS
$func$
BEGIN
IF EXISTS (SELECT 1 FROM pg_attribute
WHERE attrelid = _tbl
AND attname = _col
AND NOT attisdropped) THEN
RETURN FALSE;
ELSE
EXECUTE format('ALTER TABLE %s ADD COLUMN %I %s...
How do I select the “last child” with a specific class name in CSS? [duplicate]
How do I select the "last child" with the class name: list ?
6 Answers
6
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How to make join queries using Sequelize on Node.js
...id'})
Post.find({ where: { ...}, include: [User]})
Which will give you
SELECT
`posts`.*,
`users`.`username` AS `users.username`, `users`.`email` AS `users.email`,
`users`.`password` AS `users.password`, `users`.`sex` AS `users.sex`,
`users`.`day_birth` AS `users.day_birth`,
`users`.`mo...
How to enable MySQL Query Log?
...global general_log = 1;
SET global log_output = 'table';
View the log
select * from mysql.general_log;
Disable Query logging on the database
SET global general_log = 0;
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List of encodings that Node.js supports
...r.gz
gyp http 200 http://nodejs.org/dist/v0.10.1/node-v0.10.1.tar.gz
xcode-select: Error: No Xcode is selected. Use xcode-select -switch <path-to-xcode>, or see the xcode-select manpage (man xcode-select) for further information.
fs.readFileSync() returns a Buffer if no encoding is specified...
What columns generally make good indexes?
...earching the results speedily from tables. So it is most important step to select which columns to be indexed. There are two major places where we can consider indexing: columns referenced in the WHERE clause and columns used in JOIN clauses. In short, such columns should be indexed against which yo...