Updating a specific row in sql
SQL even has a way, a relatively new addition to the standard, by which you can insert, update, and delete all at once. For example, you want to insert a new record into the DEPT table.That may not sound like too useful a thing now, but the MERGE statement represents a very powerful way to bring a database table into sync with an external source of data (such as a flat file feed from a remote system). The value for DEPTNO should be 50, DNAME should be “PROGRAMMING”, and LOC should be “BALTIMORE”.This chapter turns the tables, and focuses on the following three topic areas: For ease in finding them when you need them, recipes in this chapter have been grouped by topic: all the insertion recipes come first, followed by the update recipes, and finally recipes for deleting data. It begins with the simple problem of inserting a single row.Many times, however, it is more efficient to use a set-based approach to create new rows.The first syntactical form, called a searched update, updates the value of one or more columns for all rows of the table for which the WHERE clause evaluates to TRUE.The second syntactical form, called a positioned update, updates one or more columns on the current row of an open, updatable cursor.Whenever you alter the value of a column referenced by the -- All the employees except the manager of -- department (WORKDEPT) 'E21' have been temporarily reassigned.
Once data has been added to a My SQL database table, it is invariably necessary to delete or update some or all of that data.The columns that are not on the list retain their original values. In some databases, such as Postgre SQL, when a FROM clause is present, what essentially happens is that the target table is joined to the tables mentioned in the fromlist, and each output row of the join represents an update operation for the target table.Firstly, it needs the name of the table that is to be updated.Secondly, it needs to know which columns are to be updated, and the new values for those columns.