From Rick_Cale@teamhealth.com Mon, 04 Feb 2002 10:28:07 -0800
From: Rick_Cale@teamhealth.com
Date: Mon, 04 Feb 2002 10:28:07 -0800
Subject: Which is more efficient For vs FORALL
Message-ID: <F001.0040527E.20020204101537@fatcity.com>
MIME-Version: 1.0
Content-Type: text/plain


Hi DBAs

Here are 2 scenario's.  Which one is more efficient?
Assume 10,000 records to update

Thanks
Rick

1. For each record update field1 with subsquery
Assume cursor is declared
  FOR cursor_rec IN new_patients_cur LOOP
      UPDATE <table>
      SET field1 =
        (SELECT value
                    FROM table
         WHERE ...)
      WHERE ....
 END LOOP;

2. For each record load nested table with data then update all records with
a single FORALL

  t_type1  IS TABLE OF table1.field1%TYPE;
  v_type1 t_type1(10000);

/* Load the PLSQL nested table */
  FOR cursor_rec IN new_patients_cur LOOP
       v_loop_ctr := v_loop_ctr + 1;
      v_type1 := cursor_rec.field1;
 END LOOP;

/* INSERT all 10,000 records with on context switch */
FORALL v_count IN 1...10000)
    UPDATE field1 = v_type1(v_count);



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