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PHP + MySQL transactions examples
...b_passwd,$db_name); // error-check this
// note: this is meant for InnoDB tables. won't work with MyISAM tables.
try {
$conn->autocommit(FALSE); // i.e., start transaction
// assume that the TABLE groups has an auto_increment id field
$query = "INSERT INTO groups (name) ";
$qu...
How to trim a string in SQL Server before 2017?
...ou add database constraints to prevent bad data in the future e.g.
ALTER TABLE Customer ADD
CONSTRAINT customer_names__whitespace
CHECK (
Names NOT LIKE ' %'
AND Names NOT LIKE '% '
AND Names NOT LIKE '% %'
);
Also consider disallowing...
SQL JOIN vs IN performance?
... faster more often than not.
So if you are only interested in values from table a you can use this query:
SELECT a.*
FROM a
WHERE EXISTS (
SELECT *
FROM b
WHERE b.col = a.col
)
The difference might be huge if col is not indexed, because the db does not have to find al...
How to show the last queries executed on MySQL?
...ontrol this option globally at runtime:
Execute SET GLOBAL log_output = 'TABLE';
Execute SET GLOBAL general_log = 'ON';
Take a look at the table mysql.general_log
If you prefer to output to a file instead of a table:
SET GLOBAL log_output = "FILE"; the default.
SET GLOBAL general_log_file = ...
iOS 7 - How to display a date picker in place in a table view?
In WWDC 2013 video, Apple suggests displaying picker in place in a table view in iOS 7. How to insert and animate a view between table view cells?
...
如何查看Oracle用户的SQL执行历史记录？ - 数据库(内核) - 清泛网 - 专注C/...
...
SQL> select username,scn,timestamp,sql_redo from v$logmnr_contents where table_name='TEST2';
SQL> select username,scn,timestamp,sql_redo from v$logmnr_contents where username='P_CHENMING';
--关闭MINER
SQL> execute dbms_logmnr.end_logmnr;
--关闭辅助日志
SQL> alter database drop suppl...
SQL Query to concatenate column values from multiple rows in Oracle
...es of the ename column (concatenated with a comma) from the employee_names table in an xml element (with tag E)
extract the text of this
aggregate the xml (concatenate it)
call the resulting column "Result"
share
|...
What does it mean by select 1 from table?
...
SELECT 1 FROM TABLE_NAME means, "Return 1 from the table". It is pretty unremarkable on its own, so normally it will be used with WHERE and often EXISTS (as @gbn notes, this is not necessarily best practice, it is, however, common enough t...
SQL Inner-join with 3 tables?
I'm trying to join 3 tables in a view; here is the situation:
12 Answers
12
...
Change a column type from Date to DateTime during ROR migration
...
First in your terminal:
rails g migration change_date_format_in_my_table
Then in your migration file:
For Rails >= 3.2:
class ChangeDateFormatInMyTable < ActiveRecord::Migration
def up
change_column :my_table, :my_column, :datetime
end
def down
change_column :my_tabl...