Update IN/EXISTS item.

1 files changed, 7 insertions, 4 deletions

diff --git a/doc/src/FAQ/FAQ.html b/doc/src/FAQ/FAQ.html
index cad83373cf8..54587662260 100644
--- a/doc/src/FAQ/FAQ.html
+++ b/doc/src/FAQ/FAQ.html
@@ -14,7 +14,7 @@
   alink="#0000ff">
     <H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
 
-    <P>Last updated: Mon Sep 30 23:28:35 EDT 2002</P>
+    <P>Last updated: Wed Oct  9 23:14:53 EDT 2002</P>
 
     <P>Current maintainer: Bruce Momjian (<A href=
     "mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR>
@@ -1282,22 +1282,25 @@ BYTEA           bytea           variable-length byte array (null-byte safe)
 
     <P>Currently, we join subqueries to outer queries by sequentially
     scanning the result of the subquery for each row of the outer
-    query. A workaround is to replace <CODE>IN</CODE> with
+    query. If the subquery returns only a few rows and the outer query
+    returns many rows, <CODE><SMALL>IN</SMALL></CODE> is fastest.  To
+    speed up other queries, replace <CODE>IN</CODE> with
     <CODE>EXISTS</CODE>:</P>
 <PRE>
 <CODE>SELECT *
     FROM tab
-    WHERE col1 IN (SELECT col2 FROM TAB2)
+    WHERE col IN (SELECT subcol FROM subtab)
 </CODE>
 </PRE>
     to: 
 <PRE>
 <CODE>SELECT *
     FROM tab
-    WHERE EXISTS (SELECT col2 FROM TAB2 WHERE col1 = col2)
+    WHERE EXISTS (SELECT subcol FROM subtab WHERE subcol = col)
 </CODE>
 </PRE>
 
+    For this to be fast, <CODE>subcol</CODE> should be an indexed column.
     We hope to fix this limitation in a future release. 
 
     <H4><A name="4.23">4.23</A>) How do I perform an outer join?</H4>