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MySQL - why not index every field?
...k about index updates were one update trigger all indexes update this is a select all unordered equivalent in time
from this I conclude that you have in this scenario that if you will loose this time is preferable to lose it in a select nor an update because if you will select a field that is not i...
Delimiters in MySQL
...TABLE tablea (
col1 INT,
col2 INT
);
INSERT INTO tablea
SELECT * FROM table1;
CREATE TABLE tableb (
col1 INT,
col2 INT
);
INSERT INTO tableb
SELECT * FROM table2;
/* whole procedure ends with the custom delimiter */
END$$
/* Finally, reset the delimiter to...
SQL Server indexes - ascending or descending, what difference does it make?
...TE 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
ORDER BY
col1, col2
An index on a single colum...
What's the best way to join on the same table twice?
...tiple times or using subqueries etc.
I would just clean things up a bit:
SELECT t.PhoneNumber1, t.PhoneNumber2,
t1.SomeOtherFieldForPhone1, t2.someOtherFieldForPhone2
FROM Table1 t
JOIN Table2 t1 ON t1.PhoneNumber = t.PhoneNumber1
JOIN Table2 t2 ON t2.PhoneNumber = t.PhoneNumber2
What i did:...
MySQL remove all whitespaces from the entire column
...
Working Query:
SELECT replace(col_name , ' ','') FROM table_name;
While this doesn't :
SELECT trim(col_name) FROM table_name;
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|
im...
How to escape single quotes in MySQL
...
Put quite simply:
SELECT 'This is Ashok''s Pen.';
So inside the string, replace each single quote with two of them.
Or:
SELECT 'This is Ashok\'s Pen.'
Escape it =)
...
How can I see the specific value of the sql_mode?
...mode. If you set it, then that query will show you the details:
mysql> SELECT @@sql_mode;
+------------+
| @@sql_mode |
+------------+
| |
+------------+
1 row in set (0.00 sec)
mysql> set sql_mode=ORACLE;
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT @@sql_mode;
+-------...
Unknown column in 'field list' error on MySQL Update query
..._user_profile.fellow = 'y'
WHERE
master_user_profile.user_id IN (
SELECT tran_user_branch.user_id
FROM tran_user_branch WHERE tran_user_branch.branch_id = 17);
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improve this a...
Types in MySQL: BigInt(20) vs Int(20)
...E TABLE foo ( bar INT(20) ZEROFILL );
INSERT INTO foo (bar) VALUES (1234);
SELECT bar from foo;
+----------------------+
| bar |
+----------------------+
| 00000000000000001234 |
+----------------------+
It's a common source of confusion for MySQL users to see INT(20) and assume ...
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.
...