Do I need to create separate index for primary key of relational database table
You don’t need to. The primary key is already an index.
database
Is it bad design to use arrays within a database?
Short answer to the title: No A bit longer answer: You should learn to use arrays when appropriate. Arrays are not bad design themselves, they are as atomic as a character varying field (array of characters, no?) and they exists to make our lives easier and our databases faster and lighter. There are issues considering … Read more
How to call the Scan variadic function using reflection
Here’s the solution that I’ve arrived at. It doesn’t get the Types before traversing the data, and so doesn’t know before hand the type of each value before pulling the values out through Scan(), but the point really is to not have to know the types before hand. The trick was to create 2 slices, … Read more
Compare structures of two databases?
For MySQL database you can compare view and tables (column name and column type) using this query: SET @firstDatabaseName=”[first database name]”; SET @secondDatabaseName=”[second database name]”; SELECT * FROM (SELECT CONCAT(cl.TABLE_NAME, ‘ [‘, cl.COLUMN_NAME, ‘, ‘, cl.COLUMN_TYPE, ‘]’) tableRowType FROM information_schema.columns cl, information_schema.TABLES ss WHERE cl.TABLE_NAME = ss.TABLE_NAME AND cl.TABLE_SCHEMA = @firstDatabaseName AND ss.TABLE_TYPE IN(‘BASE TABLE’, … Read more
Why aren’t OODBMS as widespread as RDBMS?
One reason that RDBMS has retained popularity is that it’s established technology, well understood and has a standard language (SQL) that multiple vendors support. It also has a few good interfaces like ODBC and JDBC that make it connect with different languages pretty well. A stable API is a strong factor in keeping a technology … Read more
ROW_NUMBER() without over in SQL
select ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) as number from Task order by RuleId
Local Sql database support for Windows phone 7 [closed]
There are lots of options: WinPhone7Db Perst SQLite (and here) siaqodb db4o Ninja Database Pro Rapid Repository Sterling Effiproz SQL Compact Edition will be coming in the “Mango” update – due later this year
Recover postgreSQL databases from raw physical files
If you have the whole data folder, you have everything you need (as long as architecture is the same). Just try restoring it on another machine before wiping this one out, in case you didn’t copy something. Just save the data directory to disk. When launching Postgres, set the parameter telling it where the data … Read more
How to lay out B-Tree data on disk?
https://web.archive.org/web/20161221112438/http://www.toadworld.com/platforms/oracle/w/wiki/11001.oracle-b-tree-index-from-the-concept-to-internals Notes: Databases do not directly implement indexes based on B-tree but on a variant called B+ tree. Which according to wikipedia: A B+ tree can be viewed as a B-tree in which each node contains only keys (not key-value pairs), and to which an additional level is added at the bottom with linked leaves. … Read more
Why is negative id or zero considered a bad practice?
To be clear, this question and answer are about using negative numbers for surrogate keys, not for natural keys. As far as I know, there are three reasons for considering it to be a bad practice. It violates the principle of least surprise. Some people assume all ID numbers are non-negative. Some people use negative … Read more