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Oracle LNNVL function
Oracle/PLSQL LNNVL function is used in the WHERE SQL query sentence to evaluate the state when one of the operands may contain the value NULL.
Oracle/PLSQL syntax of LNNVL function
LNNVL( condition_id )
The LNNVL function will return to the following:
| The condition is assessed as | LNNVL will return the value |
|---|---|
| TRUE | FALSE |
| FALSE | TRUE |
| UNKNOWN | TRUE |
So, if we had two columns called qty and reorder_level, where qty = 20 and reorder_level IS NULL, the function LNNVL would return the following:
| Condition | The condition is assessed as | LNNVL will return the value |
|---|---|---|
| qty = reorder_level | UNKNOWN | TRUE |
| qty IS NULL | FALSE | TRUE |
| reorder_level IS NULL | TRUE | FALSE |
| qty = 20 | TRUE | FALSE |
| reorder_level = 20 | UNKNOWN | TRUE |
LNNVL function in the following versions of Oracle/PLSQL
| Oracle 12c, Oracle 11g, Oracle 10g |
The LNNVL function can be used in Oracle PLSQL.
Let’s have a look at an example. If we had a product table containing the following data:
| PROD_ID | QTY_ID | REORDER_LEVEL_ID |
|---|---|---|
| 1000 | 20 | NULL |
| 2000 | 15 | 8 |
| 3000 | 8 | 10 |
| 4000 | 12 | 6 |
| 5000 | 2 | 2 |
| 6000 | 4 | 5 |
And we wanted to find all the products whose QTY was below REORDER_LEVEL, let’s run the next SQL query:
SELECT *
FROM prods
WHERE QTY < REORDER_LEVEL;
The request will return the following result:
| PROD_ID | QTY_ID | REORDER_LEVEL_ID |
|---|---|---|
| 3000 | 8 | 10 |
| 6000 | 4 | 5 |
However, if we wanted to consider products that were lower than REORDER_LEVEL and REORDER_LEVEL had the value NULL, we would use the function LNNVL as follows:
SELECT *
FROM prods
WHERE LNNVL(QTY >= REORDER_LEVEL);
This will return the next result:
| PROD_ID | QTY_ID | REORDER_LEVEL_ID |
|---|---|---|
| 1000 | 20 | NULL |
| 3000 | 8 | 10 |
| 6000 | 4 | 5 |
In this example, the resulting set also contains prod_id 1000, which has REORDER_LEVEL NULL.
LNNVL FUNCTION IN ORACLE SQL
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