- "http://www.PostgreSQL.org/users-lounge/docs/programmer/odbc.htm">ODBC chapter
- of the Programmer's Guide.
+ "http://www.PostgreSQL.org/users-lounge/docs/programmer/odbc.htm">ODBC
+ chapter of the Programmer's Guide.
2.2) What tools are available for using
PostgreSQL with Web pages?
Maximum number of indexes on a table? unlimited
Of course, these are not actually unlimited, but limited to
- available disk space and memory/swap space. Performance may
- suffer when these values get unusually large.
+ available disk space and memory/swap space. Performance may suffer
+ when these values get unusually large.
The maximum table size of 16TB does not require large file
- support from the operating system. Large tables are stored
- as multiple 1GB files.
-
+ support from the operating system. Large tables are stored as
+ multiple 1GB files.
+
The maximum table size and maximum number of columns can be
increased by a factor of four if the default block size is
- increased to 32k.
+ increased to 32k.
4.7) How much database disk space is required
to store data from a typical text file?
Indexes do not require as much overhead, but do contain the data
that is being indexed, so they can be large also.
-
4.8) How do I find out what tables or
- indexes are defined in the database?
+
4.8) How do I find out what tables or indexes
+ are defined in the database?
psql has a variety of backslash commands to show such
information. Use \? to see them.
The ~ operator does regular expression matching, and
~* does case-insensitive regular expression matching. The
- case-insensitive variant of LIKE
- is called ILIKE.
+ case-insensitive variant of LIKE is called
+ ILIKE.
4.14) In a query, how do I detect if a field
is NULL?
SELECT *
FROM t1 LEFT OUTER JOIN t2 ON (t1.col = t2.col);
-or
+ or
SELECT *
FROM t1 LEFT OUTER JOIN t2 USING (col);
- These identical queries join t1.col to t2.col, and also return any
- unjoined rows in t1 (those with no match in t2). A
+
+
These identical queries join t1.col to t2.col, and also return
+ any unjoined rows in t1 (those with no match in t2). A
RIGHT join would add unjoined rows of t2. A
FULL join would return the matched rows plus all
unjoined rows from t1 and t2. The word OUTER is
joining tab1 and tab2, the following query does an
outer join of the two tables:
-
+
SELECT tab1.col1, tab2.col2
FROM tab1, tab2
compiler compute the dependencies automatically.