How to Perform Dynamic Pivots in Oracle SQL with Varying Values?

Oracle SQL Dynamic Pivot Table: Coping with Changing Values

Handling dynamic values ​​in IN statements can be tricky when using the PIVOT function in Oracle SQL. This article provides a solution.

Oracle's PIVOT usually requires the use of static value strings in the IN statement, for example:

<code class="language-sql">... pivot (sum(A) for B in (X))  </code>

However, if the value of B is stored in a database column and updated regularly, manually updating the string X becomes impractical.

To solve this problem, we can use a trick which involves creating a IN string and then using it in the PIVOT query. Let’s break it down:

Step 1: Build the IN string

To create a string, we use the COLUMN NEW_VALUE and LISTAGG functions as follows:

<code class="language-sql">COLUMN temp_in_statement new_value str_in_statement
SELECT DISTINCT 
    LISTAGG('''' || myLetter || ''' AS ' || myLetter,',')
        WITHIN GROUP (ORDER BY myLetter) AS temp_in_statement 
    FROM (SELECT DISTINCT myLetter FROM myTable);</code>

This query builds a string similar to:

<code>'A' AS A,'B' AS B,'C' AS C</code>

Step 2: Using strings in PIVOT

Now we can add this string to our PIVOT query:

<code class="language-sql">SELECT * FROM 
    (SELECT myNumber, myLetter, myValue FROM myTable)
    PIVOT (Sum(myValue) AS val FOR myLetter IN (&str_in_statement));</code>

Restrictions:

While this method provides a solution, it has a limitation: the maximum length of the connection string is 4000 bytes. Therefore, this method may not be suitable if the number of values ​​of B is very large.

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