大约有 6,000 项符合查询结果（耗时：0.0147秒） [XML]
What is the string concatenation operator in Oracle?
What is the string concatenation operator in Oracle SQL?
5 Answers
5
...
Backup/Restore a dockerized PostgreSQL database
I'm trying to backup/restore a PostgreSQL database as is explained on the Docker website, but the data is not restored.
10 ...
Add primary key to existing table
...imary key,otherwise will cause error. Because there is one primary key for sql table.
First, you have to drop your old primary key.
MySQL:
ALTER TABLE Persion
DROP PRIMARY KEY;
SQL Server / Oracle / MS Access:
ALTER TABLE Persion
DROP CONSTRAINT 'constraint name';
You have to find the con...
Http长连接200万尝试及调优 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...撑的连接数个数，而并非qps，当然qps也是我们需要考虑的性能点之一。这种应用常见于消息推送系统，也称为comet应用，比如聊天室或即时消息推送系统等。comet应用具体可见我之前的介绍，在此不多讲。对于这类系统，因为很...
Possible to do a MySQL foreign key to one of two possible tables?
...s not possible
);
There's no way to model Polymorphic Associations using SQL constraints. A foreign key constraint always references one target table.
Polymorphic Associations are supported by frameworks such as Rails and Hibernate. But they explicitly say that you must disable SQL constraints ...
Ant task to run an Ant target only if a file exists?
...
Check Using Filename filters like DB_*/**/*.sql
Here is a variation to perform an action if one or more files exist corresponding to a wildcard filter. That is, you don't know the exact name of the file.
Here, we are looking for "*.sql" files in any sub-directories ...
How do you count the number of occurrences of a certain substring in a SQL varchar?
...e a,b,c,d. Is there a way to count the number of commas in that value in T-SQL?
20 Answers
...
SQL join on multiple columns in same tables
...new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f16597660%2fsql-join-on-multiple-columns-in-same-tables%23new-answer', 'question_page');
}
);
Post as a guest
...
How to turn off the Eclipse code formatter for certain sections of Java code?
I've got some Java code with SQL statements written as Java strings (please no OR/M flamewars, the embedded SQL is what it is - not my decision).
...
How to copy data from one table to another new table in MySQL?
I want to copy data from one table to another in MySQL.
11 Answers
11
...