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Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/datatype.sgml | 50 |
1 files changed, 36 insertions, 14 deletions
diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml index bbbc85197bb..e86614f2ef7 100644 --- a/doc/src/sgml/datatype.sgml +++ b/doc/src/sgml/datatype.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.54 2001/05/21 16:54:45 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.55 2001/05/22 16:37:15 petere Exp $ --> <chapter id="datatype"> @@ -2276,30 +2276,52 @@ SELECT * FROM test1 WHERE a; Bit strings are strings of 1's and 0's. They can be used to store or visualize bit masks. There are two SQL bit types: <type>BIT(<replaceable>x</replaceable>)</type> and <type>BIT - VARYING(<replaceable>x</replaceable>)</type>; the - <replaceable>x</replaceable> specifies the maximum length. - <type>BIT</type> type data is automatically padded with 0's on the - right to the maximum length, <type>BIT VARYING</type> is of - variable length. <type>BIT</type> without length is equivalent - to <literal>BIT(1)</literal>, <type>BIT VARYING</type> means - unlimited length. Input data that is longer than the allowed - length will be truncated. Refer to <xref + VARYING(<replaceable>x</replaceable>)</type>; where + <replaceable>x</replaceable> is a positive integer. + </para> + + <para> + <type>BIT</type> type data must match the length + <replaceable>x</replaceable> exactly; it is an error to attempt to + store shorter or longer bit strings. <type>BIT VARYING</type> is + of variable length up to the maximum length + <replaceable>x</replaceable>; longer strings will be rejected. + <type>BIT</type> without length is equivalent to + <literal>BIT(1)</literal>, <type>BIT VARYING</type> without length + specification means unlimited length. + </para> + + <note> + <para> + Prior to PostgreSQL 7.2, <type>BIT</type> type data was + zero-padded on the right. This was changed to comply with the + SQL standard. To implement zero-padded bit strings, a + combination of the concatenation operator and the + <function>substring</function> function can be used. + </para> + </note> + + <para> + Refer to <xref linkend="sql-syntax-bit-strings"> for information about the syntax of bit string constants. Bit-logical operators and string manipulation functions are available; see <xref linkend="functions">. </para> - <informalexample> - <para> - Some examples: + <example> + <title>Using the bit string types</title> + <programlisting> CREATE TABLE test (a BIT(3), b BIT VARYING(5)); INSERT INTO test VALUES (B'101', B'00'); +INSERT INTO test VALUES (B'10', B'101'); +<computeroutput> +ERROR: bit string length does not match type bit(3) +</computeroutput> SELECT SUBSTRING(b FROM 1 FOR 2) FROM test; </programlisting> - </para> - </informalexample> + </example> </sect1> |