Auto added space in field while updating table in database
A secondary benefit from indexing the unique key column is the query performance boost this operation gives to the joins or searches executed on the unique key column.
Overall, I would estimate that such issues account for around 80% of the problems that a DBA team faces on a weekly basis.Foreign key columns are usually nonunique because they're on the "many" side of the one-to-many (1: M) relationship.Therefore, you expect to see duplicate values in the foreign key column every time one row in the master table (on the "one" side) is related to two or more rows in the detail table (on the "many" side).If no key column is specified, the primary key columns are used to find the row.If more than one row per new row is affected, an exception is thrown.You need to create a unique index on a foreign key column only if you're enforcing a mandatory one-to-one (1:1) relationship between two tables.
In a 1:1 relationship, the values in the foreign key column are a unique set that corresponds to the primary key values in the master table.
We can connect to Google Cloud SQL, DB2, Derby, H2, HSQLDB, My SQL, an ODBC connection, Oracle, Postgre SQL, SQL Server (and Microsoft Azure Database), or SQLite an Sybase.
For every database system, different options will be available for configuring the connection.
Rodney describes, with some feeling, the errors that can lead to this sort of crisis for the working DBA, and their solution.
When I look back over my career as a SQL Server DBA, analyzing the kinds of issues that I have had to resolve, usually under pressure, nothing brings me out in a colder sweat than the runaway data, log or Temp DB file.
Indexing is such a large subject that getting a handle on what to do and what not to do when you're developing your indexing strategies can be difficult. Everyone—from product vendors to database-performance specialists to DBAs who work on the production front lines—has ideas about how and when to index. Make certain that the primary key for each table and any unique key columns that exist are indexed.