更新语句的性能提升

Question

I need to update all the columns in a table using the trimmed version of the same columns. Table has 130 columns and 5 million records. And the query is running more than 3 hours without any sign of completion.

Begin 
    UPDATE table
       SET column = TRIM(column)
     WHERE date = '01-01-21';
    .
     ..
      ..
    Commit;
End;
/

Kindly help in improving the performance of this query. PS: none of the columns have any index.

Answer 1

Don't use PL/SQL but SQL:

update that_table set
  col1 = trim(col1),
  col2 = trim(col2),
  ...
  col130 = trim(col130)
where date_column = date '2021-01-01';

Column in where clause should - probably - only be indexed as you're filtering on it. If you're updating the whole table, you don't need where clause at all.

Also, if that column's datatype is date , then use date literal or to_date function with appropriate format model, ie don't force Oracle to implicitly convert string (that's '01-01-21' to date and spend some time doing so.