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Update FAQ.

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Bruce Momjian 2000-06-24 01:51:33 +00:00
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doc/FAQ
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@ -102,6 +102,7 @@
Why?
4.22) How do I create a column that will default to the current time?
4.23) Why are my subqueries using IN so slow?
4.24) How do I do an outer join?
Extending PostgreSQL
@ -334,11 +335,11 @@
Features
PostgreSQL has most features present in large commercial
DBMS's, like transactions, subselects, triggers, views, and
sophisticated locking. We have some features they don't have,
like user-defined types, inheritance, rules, and multi-version
concurrency control to reduce lock contention. We don't have
foreign key referential integrity or outer joins, but are
DBMS's, like transactions, subselects, triggers, views, foreign
key referential integrity, and sophisticated locking. We have
some features they don't have, like user-defined types,
inheritance, rules, and multi-version concurrency control to
reduce lock contention. We don't have outer joins, but are
working on them for our next release.
Performance
@ -395,10 +396,10 @@
2.1) Are there ODBC drivers for PostgreSQL?
There are two ODBC drivers available, PostODBC and OpenLink ODBC.
There are two ODBC drivers available, PsqlODBC and OpenLink ODBC.
PostODBC is included in the distribution. More information about it
can be gotten from: http://www.insightdist.com/psqlodbc
PsqlODBC is included in the distribution. More information about it
can be gotten from: ftp://ftp.postgresql.org/pub/odbc/index.html
OpenLink ODBC can be gotten from http://www.openlinksw.com. It works
with their standard ODBC client software so you'll have PostgreSQL
@ -409,6 +410,8 @@
commercial-quality support, but a freeware version will always be
available. Questions to postgres95@openlink.co.uk.
See also the ODBC chapter of the Programmer's Guide.
2.2) What tools are available for hooking PostgreSQL to Web pages?
A nice introduction to Database-backed Web pages can be seen at:
@ -971,12 +974,9 @@ BYTEA bytea variable-length array of bytes
4.22) How do I create a column that will default to the current time?
This way always works:
Use now():
CREATE TABLE test (x int, modtime timestamp default now() );
In releases 7.0 and later, you may use:
create table test (x int, modtime timestamp default 'now');
4.23) Why are my subqueries using IN so slow?
Currently, we join subqueries to outer queries by sequential scanning
@ -992,6 +992,21 @@ BYTEA bytea variable-length array of bytes
WHERE EXISTS (SELECT col2 FROM TAB2 WHERE col1 = col2)
We hope to fix this limitation in a future release.
4.24) How do I do an outer join?
PostgreSQL does not support outer joins in the current release. They
can be simulated using UNION and NOT IN. For example, when joining
tab1 and tab2, the following query does an outer join of the two
tables:
SELECT tab1.col1, tab2.col2
FROM tab1, tab2
WHERE tab1.col1 = tab2.col1
UNION ALL
SELECT tab1.col1, NULL
FROM tab1
WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2)
ORDER BY tab1.col1
_________________________________________________________________
Extending PostgreSQL