To transpose rows to columns in PostgreSQL, you can use the crosstab function from the tablefunc extension. Here are the steps to follow:

  1. Enable the tablefunc extension if it's not already enabled. You can do this by running the following command as a superuser in your PostgreSQL database:

    sql
    CREATE EXTENSION IF NOT EXISTS tablefunc;
  2. Create a query that selects the data you want to transpose. The query should return three columns: the category, the row identifier, and the value. For example:

    sql
    SELECT category, row_identifier, value FROM your_table;
  3. Use the crosstab function to transpose the rows to columns. The crosstab function takes two parameters: the first is the initial query, and the second is a SQL string that defines the column names for the transposed data. For example:

    sql
    SELECT * FROM crosstab( 'SELECT category, row_identifier, value FROM your_table', 'VALUES (''column1''), (''column2''), (''column3'')' ) AS ct(category text, column1 text, column2 text, column3 text);

    In the above example, we assume that you want to transpose the rows to three columns named "column1", "column2", and "column3". Adjust the SQL string inside the VALUES clause to match your desired column names.

  4. Execute the query to get the transposed result.

Note that the number and names of the columns in the crosstab function should match the expected output columns in the transposed result. Make sure to adjust them accordingly in your query.

Also, keep in mind that the crosstab function requires a fixed set of columns for the transposed data. If your data has a dynamic number of columns, you might need to use dynamic SQL or a different approach to achieve the transposition.

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