How does Oracle convert multiple rows of data into one row?

In Oracle, you can use aggregate functions and conditional expressions to convert multiple rows of data into one row. Here are two commonly used methods:

1. Use the LISTAGG function:

SELECT LISTAGG(column_name, ', ') WITHIN GROUP (ORDER BY column_name) AS combined_data
FROM table_name;

In this case, column_name is the name of the column to be merged, and table_name is the name of the table to be queried.

1. Use CASE statements and aggregation functions.

SELECT MAX(CASE WHEN condition1 THEN column1 END) AS column1,
       MAX(CASE WHEN condition2 THEN column2 END) AS column2,
       ...
       MAX(CASE WHEN conditionN THEN columnN END) AS columnN
FROM table_name;

In this case, the condition refers to the conditional expression, the column is the name of the column being merged, and the table_name is the name of the table to be queried.

Please choose a method suitable for your specific situation.