Select where null oracle

We use null to just check for the existence of rows, we don't care about getting data. The 'select null' in the correlated subquery is a commonly used syntax because the column data returned is irrelevant. Instead the fact that a single row meets the join crieria is what is important with the EXISTS clause - this is what will trigger the inclusion of a row in the outer query. You will also see other vairations of this theme e. December 26, - am UTC. Why not this way?? A reader, December 27, - pm UTC.

Tom, The same query can be written like this: select distinct dept. LOC from dept,emp where emp. DNAME, dept. The coalesce function returns the first non-NULL value of the expressions in the list. The list must consist of at least 2 values. 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 is done on insert only. If you modify the default during the life of the table, the new default will be applied from that moment on. Now how do you make sure a default is applied to columns already NULL?

It can for instance be used to build a decision table. Consider the following decision table:. The column in our table just holds the code instead of the value. If we want to represent the value instead of the code we could write a query like this:. The case statement has two flavors. The simple case and the searched case.

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. This can be helpful when you need to choose from a set of distinct values. In the searched case every case has its own expression. This can for instance be helpful when using ranges. The else clause is optional.

NULL values are one of the most mind-boggling values in the Oracle database. Here it is replacing the null values with empty space. I did not understand the question — ScaisEdge. There is a value as "Null" and I want it to be empty. So I just replacing this null value with empty space ' '. Show 2 more comments. Son Ha Son Ha 81 1 1 silver badge 2 2 bronze badges. Matt Ke 2, 8 8 gold badges 26 26 silver badges 41 41 bronze badges.

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