diff options
Diffstat (limited to 'doc/src/sgml/datatype.sgml')
| -rw-r--r-- | doc/src/sgml/datatype.sgml | 68 |
1 files changed, 49 insertions, 19 deletions
diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml index 41ca3c00e53..28d3fcb7ede 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 1.102 2002/08/23 02:54:18 momjian Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.103 2002/09/18 21:35:20 tgl Exp $ --> <chapter id="datatype"> @@ -823,8 +823,19 @@ CREATE TABLE <replaceable class="parameter">tablename</replaceable> ( <note> <para> - Prior to <productname>PostgreSQL</> 7.2, strings that were too long were silently - truncated, no error was raised. + If one explicitly casts a value to + <type>character(<replaceable>n</>)</type> or <type>character + varying(<replaceable>n</>)</type>, then an overlength value will + be truncated to <replaceable>n</> characters without raising an + error. (This too is required by the SQL standard.) + </para> + </note> + + <note> + <para> + Prior to <productname>PostgreSQL</> 7.2, strings that were too long were + always truncated without raising an error, in either explicit or + implicit casting contexts. </para> </note> @@ -897,12 +908,14 @@ INSERT INTO test2 VALUES ('ok'); INSERT INTO test2 VALUES ('good '); INSERT INTO test2 VALUES ('too long'); <computeroutput>ERROR: value too long for type character varying(5)</computeroutput> +INSERT INTO test2 VALUES ('too long'::varchar(5)); -- explicit truncation SELECT b, char_length(b) FROM test2; <computeroutput> b | char_length -------+------------- ok | 2 good | 5 + too l | 5 </computeroutput> </programlisting> <calloutlist> @@ -932,7 +945,7 @@ SELECT b, char_length(b) FROM test2; </para> <table tocentry="1"> - <title>Specialty Character Type</title> + <title>Specialty Character Types</title> <tgroup cols="3"> <thead> <row> @@ -2832,29 +2845,39 @@ SELECT * FROM test1 WHERE a; <para> 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>; where - <replaceable>x</replaceable> is a positive integer. + <type>BIT(<replaceable>n</replaceable>)</type> and <type>BIT + VARYING(<replaceable>n</replaceable>)</type>, where + <replaceable>n</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 + <replaceable>n</replaceable> exactly; it is an error to attempt to + store shorter or longer bit strings. <type>BIT VARYING</type> data 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 + <replaceable>n</replaceable>; longer strings will be rejected. + Writing <type>BIT</type> without a length is equivalent to + <literal>BIT(1)</literal>, while <type>BIT VARYING</type> without a length specification means unlimited length. </para> <note> <para> - Prior to <productname>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. + If one explicitly casts a bit-string value to + <type>BIT(<replaceable>n</>)</type>, it will be truncated or + zero-padded on the right to be exactly <replaceable>n</> bits, + without raising an error. Similarly, + if one explicitly casts a bit-string value to + <type>BIT VARYING(<replaceable>n</>)</type>, it will be truncated + on the right if it is more than <replaceable>n</> bits. + </para> + </note> + + <note> + <para> + Prior to <productname>PostgreSQL</> 7.2, <type>BIT</type> data was + always silently truncated or zero-padded on the right, with or without an + explicit cast. This was changed to comply with the SQL standard. </para> </note> @@ -2874,9 +2897,16 @@ 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) +ERROR: Bit string length 2 does not match type BIT(3) +</computeroutput> +INSERT INTO test VALUES (B'10'::bit(3), B'101'); +SELECT * FROM test; +<computeroutput> + a | b +-----+----- + 101 | 00 + 100 | 101 </computeroutput> -SELECT SUBSTRING(b FROM 1 FOR 2) FROM test; </programlisting> </example> |