Question

I want rename all column names to lower case in PostgreSQL database I have just coded a sql function. Below is the code.

CREATE OR REPLACE FUNCTION update_column_names() RETURNS boolean AS $$
DECLARE 
aRow RECORD;
aRow2 RECORD;
tbl_name TEXT;
col_name TEXT;
new_col_name TEXT; 
BEGIN
    FOR aRow IN select table_name from information_schema.tables where table_schema='public' and table_type='BASE TABLE' LOOP
        SELECT aRow.table_name INTO tbl_name from current_catalog;
        FOR aRow2 IN select column_name from information_schema.columns where table_schema='public' and table_name = aRow.table_name LOOP
            SELECT aRow2.column_name INTO col_name from current_catalog;
            new_col_name:=lower(col_name);
            RAISE NOTICE 'Table name:%',tbl_name;
            RAISE NOTICE 'Column name:%',aRow2.column_name;
            RAISE NOTICE 'New column name:%',new_col_name;
            ALTER TABLE tbl_name RENAME COLUMN col_name TO new_col_name;
        END LOOP;
    END LOOP;
    RETURN true;
END;
$$ LANGUAGE plpgsql;

The code above gives relation tbl_name does not exists. What is wrong with the code?

Answer 1

You need to use dynamic SQL to do that; the table name can’t be a variable.

⋮
EXECUTE 'ALTER TABLE ' || quote_ident(tbl_name) || ' RENAME COLUMN '
        || quote_ident(col_name) || ' TO ' || quote_ident(new_col_name);
⋮

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