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MySQL, Check if a column exists in a table with SQL
I am trying to write a query that will check if a specific table in MySQL has a specific column, and if not — create it. Otherwise do nothing. This is really an easy procedure in any enterprise-class database, yet MySQL seems to be an exception.
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MySQL - force not to use cache for testing speed of query
I'm testing the speed of some queries in MySQL. The database is caching these queries making it difficult for me to get reliable results when testing how fast these queries are.
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Maximum number of records in a MySQL database table
What is the upper limit of records for MySQL database table. I'm wondering about autoincrement field. What would happen if I add milions of records? How to handle this kind of situations?
Thx!
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How do I specify unique constraint for multiple columns in MySQL?
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For those people using MySQL workbench: go to the Indexes tab and select UNIQUE as your type. Give your index a name and check the appropriate columns under the section "Index Columns"
– Pakman
Jun 3 '13 at 2...
使用Activity启动器组件 · App Inventor 2 中文网
...频
选择联系人
启动其他外部应用程序
了解如何设置 ActivityStarter 属性
在应用程序之间传递值
将活动启动器与两个 App Inventor 应用程序一起使用
该应用程序在设备上可用吗？
附录：为设计...
“Incorrect string value” when trying to insert UTF-8 into MySQL via JDBC?
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MySQL's utf8 permits only the Unicode characters that can be represented with 3 bytes in UTF-8. Here you have a character that needs 4 bytes: \xF0\x90\x8D\x83 (U+10343 GOTHIC LETTER SAUIL).
If you have MySQL 5.5 or later you...
how to concatenate two dictionaries to create a new one in Python? [duplicate]
...ems() for d in (d1, d2, d3)))
and:
from itertools import chain
def dict_union(*args):
return dict(chain.from_iterable(d.items() for d in args))
Python 2.6 & 2.7
from itertools import chain
dict(chain.from_iterable(d.iteritems() for d in (d1, d2, d3))
Output:
>>> from iterto...
PHP + MySQL transactions examples
I really haven't found normal example of PHP file where MySQL transactions are being used. Can you show me simple example of that?
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What is this operator in MySQL?
...ard and therefore supported on other databases, unlike <=>, which is MySQL-specific.
You can think of them as specialisations of MySQL's <=>:
'a' IS NULL ==> 'a' <=> NULL
'a' IS NOT NULL ==> NOT('a' <=> NULL)
Based on this, your particular query (fragment) can be c...
Display open transactions in MySQL
...transactions and commit or cancel them?
There is no open transaction, MySQL will rollback the transaction upon disconnect.
You cannot commit the transaction (IFAIK).
You display threads using
SHOW FULL PROCESSLIST
See: http://dev.mysql.com/doc/refman/5.1/en/thread-information.html
It...