Oracle plsql if updating

17-May-2017 14:38

Consider another table STUDENT_N, which holds updates for the target table STUDENT.Every week, table STUDENT needs to be synchronized with the data in STUDENT_N – any new entries for students who attempted the GMAT to be inserted, plus corrections if any made to the existing details.Examples: NULLIF(‘A’,’B’) results in A NULLIF(‘A’,’A’) results in NULL NULLIF(2,3) results in 2 NULLIF(2,2) results in NULL NULLIF(‘2’,2) results in an error NULLIF(2,’2’) results in an error Syntax: The coalesce function returns the first non-NULL value of the expressions in the list. If all expressions evaluate to NULL then NULL is returned.Examples: COALESCE(‘A’,’B’,’C’) results in A COALESCE(NULL,’B’,’C’) results in B COALESCE(NULL, NULL,’C’) results in C COALESCE(NULL,’B’, NULL) results in B COALESCE(‘A’) results in an error Syntax: The LNNVL function is used in the WHERE clause of an SQL statement when one of the operands may contain a NULL value.When matched, set transaction_type = ‘U’, when not matched, set it to ‘I’. After running MERGE, select the ids based on transaction type. That’s then 2 queries; in my case I have just to treat one row at a time (update 1 or insert 1) so the simplest for me is probably to do a fist get query to check if the row already exists and then depending on the result do an insert or an update (in both cases the RETURNING clause works fine. PS: just fyi, my app has to support several SQL servers and in My Sql it’s much simpler: 1 single query thanks to the “ON DUPLICATE KEY UPDATE” instruction.Hmmm…looks like you’ll have to do the traditional INSERT/UPDATE as you say.The function returns TRUE is the result of the condition is FALSE and FALSE is the result of the condition is TRUE or UNKNOWN.

update existing rows in a table or insert new rows depending on a match condition.

The following queries have the same result: Note that the condition must be inverted when using the LNNVL function. In the simple case the expression is written only once and depending on the result of this expression one of the possible cases is being used.

When a column in a table is defined there is the possibility to have a default value for this column whenever it is inserted without a value. This can be helpful when you need to choose from a set of distinct values.

The same query as above can be written using a simple case expression. If none of the cases is valid for the expression, then NULL is returned, as opposed to PL/SQL where an error is raised.

NULL values are one of the most mind-boggling values in the Oracle database.

update existing rows in a table or insert new rows depending on a match condition.The following queries have the same result: Note that the condition must be inverted when using the LNNVL function. In the simple case the expression is written only once and depending on the result of this expression one of the possible cases is being used.When a column in a table is defined there is the possibility to have a default value for this column whenever it is inserted without a value. This can be helpful when you need to choose from a set of distinct values.The same query as above can be written using a simple case expression. If none of the cases is valid for the expression, then NULL is returned, as opposed to PL/SQL where an error is raised.NULL values are one of the most mind-boggling values in the Oracle database.The art of doing mathematics consists in finding that special case which contains all the germs of generality. In the one before it, it was possible to convert 2 to a varchar2 value.