大约有 40,000 项符合查询结果（耗时：0.0302秒） [XML]
How to list all users in a Linux group?
...
Unfortunately, there is no good, portable way to do this that I know of. If you attempt to parse /etc/group, as others are suggesting, you will miss users who have that group as their primary group and anyone who has been added to that group via a mechanism ot...
Remove Primary Key in MySQL
I have the following table schema which maps user_customers to permissions on a live MySQL database:
12 Answers
...
When to Redis? When to MongoDB? [closed]
... need to change your schema quickly.
Because there is no schema! Altering tables in traditional, relational DBMS is painfully expensive and slow. MongoDB solves this problem by not making a lot of assumptions on your underlying data. Nevertheless, it tries to optimize as far as possible without req...
Python's json module, converts int dictionary keys to strings
...e.
In Python (and apparently in Lua) the keys to a mapping (dictionary or table, respectively) are object references. In Python they must be immutable types, or they must be objects which implement a __hash__ method. (The Lua docs suggest that it automatically uses the object's ID as a hash/key ...
Use email address as primary key?
...ies with multiple joins.
If you store information about users in multiple tables, the foreign keys to the users table will be the e-mail address. That means that you store the e-mail address multiple times.
share
|...
How to speed up insertion performance in PostgreSQL
I am testing Postgres insertion performance. I have a table with one column with number as its data type. There is an index on it as well. I filled the database up using this query:
...
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) ";
$qu...
Save PL/pgSQL output from PostgreSQL to a CSV file
...rticular directory, for instance, and the filename might have to have a suitable prefix or extension.
Which tables should the user be able to read/write in the database? This would normally be defined by GRANTs in the database, but the function is now running as a superuser, so tables which would no...
如何查看Oracle用户的SQL执行历史记录？ - 数据库(内核) - 清泛网 - 专注C/...
...
SQL> select username,scn,timestamp,sql_redo from v$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 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...