Hints and tips on database
These are some helpful hints on various topics.
apache
bash
cmd
database
java
javascript
linux
mod_rewrite
mssql
mysql
oracle
os
perl
php
regex
rsync
ssh
unix
web_design
windows
MSQQL count(columnt) doesn't support all data types
In MSSQL queries like
select count(col1) from table1
will fail if column type is uniqueidentifier, text, image, ntext. Those types are not supported also in aggregate functions and subqueries.
Oracle dual table or how to migrate Mysql tableless queries
If you are familiar with Mysql, you probably use sometimes tableless queries like this:SELECT 12 * (1 + 10);
Well, if you're migrating to Oracle you'll be surprised to find that those queries are not allowed here. The solution? Use the dual table like this:
SELECT 12 * (1 + 10) from dual
Dual is special table that is automatically created. Its schema has only one column called dummy, and is populated with just one row with value 'X'. In short - this makes it very useful for our case.
