diff options
Diffstat (limited to 'doc/src/sgml/syntax.sgml')
| -rw-r--r-- | doc/src/sgml/syntax.sgml | 38 |
1 files changed, 19 insertions, 19 deletions
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml index 65c29b835cc..9e086a58a7c 100644 --- a/doc/src/sgml/syntax.sgml +++ b/doc/src/sgml/syntax.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.111 2006/10/22 03:03:41 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.112 2007/01/31 20:56:19 momjian Exp $ --> <chapter id="sql-syntax"> <title>SQL Syntax</title> @@ -120,7 +120,7 @@ INSERT INTO MY_TABLE VALUES (3, 'hi there'); key word can be letters, underscores, digits (<literal>0</literal>-<literal>9</literal>), or dollar signs (<literal>$</>). Note that dollar signs are not allowed in identifiers - according to the letter of the SQL standard, so their use may render + according to the letter of the SQL standard, so their use might render applications less portable. The SQL standard will not define a key word that contains digits or starts or ends with an underscore, so identifiers of this @@ -466,7 +466,7 @@ $function$ digits (0 through 9). At least one digit must be before or after the decimal point, if one is used. At least one digit must follow the exponent marker (<literal>e</literal>), if one is present. - There may not be any spaces or other characters embedded in the + There cannot be any spaces or other characters embedded in the constant. Note that any leading plus or minus sign is not actually considered part of the constant; it is an operator applied to the constant. @@ -537,7 +537,7 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> ) The string constant's text is passed to the input conversion routine for the type called <replaceable>type</replaceable>. The result is a constant of the indicated type. The explicit type - cast may be omitted if there is no ambiguity as to the type the + cast can be omitted if there is no ambiguity as to the type the constant must be (for example, when it is assigned directly to a table column), in which case it is automatically coerced. </para> @@ -553,7 +553,7 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> ) <synopsis> <replaceable>typename</replaceable> ( '<replaceable>string</replaceable>' ) </synopsis> - but not all type names may be used in this way; see <xref + but not all type names can be used in this way; see <xref linkend="sql-syntax-type-casts"> for details. </para> @@ -650,7 +650,7 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> ) A dollar sign (<literal>$</literal>) followed by digits is used to represent a positional parameter in the body of a function definition or a prepared statement. In other contexts the - dollar sign may be part of an identifier or a dollar-quoted string + dollar sign can be part of an identifier or a dollar-quoted string constant. </para> </listitem> @@ -743,7 +743,7 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> ) where the comment begins with <literal>/*</literal> and extends to the matching occurrence of <literal>*/</literal>. These block comments nest, as specified in the SQL standard but unlike C, so that one can - comment out larger blocks of code that may contain existing block + comment out larger blocks of code that might contain existing block comments. </para> @@ -766,7 +766,7 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> ) associativity of the operators in <productname>PostgreSQL</>. Most operators have the same precedence and are left-associative. The precedence and associativity of the operators is hard-wired - into the parser. This may lead to non-intuitive behavior; for + into the parser. This can lead to non-intuitive behavior; for example the Boolean operators <literal><</> and <literal>></> have a different precedence than the Boolean operators <literal><=</> and <literal>>=</>. Also, you will @@ -1101,7 +1101,7 @@ SELECT 3 OPERATOR(pg_catalog.+) 4; the key words <literal>NEW</literal> or <literal>OLD</literal>. (<literal>NEW</literal> and <literal>OLD</literal> can only appear in rewrite rules, while other correlation names can be used in any SQL statement.) - The correlation name and separating dot may be omitted if the column name + The correlation name and separating dot can be omitted if the column name is unique across all the tables being used in the current query. (See also <xref linkend="queries">.) </para> </sect2> @@ -1171,7 +1171,7 @@ CREATE FUNCTION dept(text) RETURNS dept <para> In general the array <replaceable>expression</replaceable> must be - parenthesized, but the parentheses may be omitted when the expression + parenthesized, but the parentheses can be omitted when the expression to be subscripted is just a column reference or positional parameter. Also, multiple subscripts can be concatenated when the original array is multidimensional. @@ -1206,7 +1206,7 @@ $1[10:42] <para> In general the row <replaceable>expression</replaceable> must be - parenthesized, but the parentheses may be omitted when the expression + parenthesized, but the parentheses can be omitted when the expression to be selected from is just a table reference or positional parameter. For example, @@ -1277,7 +1277,7 @@ sqrt(2) <para> The list of built-in functions is in <xref linkend="functions">. - Other functions may be added by the user. + Other functions can be added by the user. </para> </sect2> @@ -1334,12 +1334,12 @@ sqrt(2) <para> The predefined aggregate functions are described in <xref - linkend="functions-aggregate">. Other aggregate functions may be added + linkend="functions-aggregate">. Other aggregate functions can be added by the user. </para> <para> - An aggregate expression may only appear in the result list or + An aggregate expression can only appear in the result list or <literal>HAVING</> clause of a <command>SELECT</> command. It is forbidden in other clauses, such as <literal>WHERE</>, because those clauses are logically evaluated before the results @@ -1407,7 +1407,7 @@ CAST ( <replaceable>expression</replaceable> AS <replaceable>type</replaceable> </para> <para> - An explicit type cast may usually be omitted if there is no ambiguity as + An explicit type cast can usually be omitted if there is no ambiguity as to the type that a value expression must produce (for example, when it is assigned to a table column); the system will automatically apply a type cast in such cases. However, automatic casting is only done for @@ -1510,7 +1510,7 @@ SELECT ARRAY[1,2,3+4]; <para> Multidimensional array values can be built by nesting array constructors. - In the inner constructors, the key word <literal>ARRAY</literal> may + In the inner constructors, the key word <literal>ARRAY</literal> can be omitted. For example, these produce the same result: <programlisting> @@ -1634,7 +1634,7 @@ SELECT ROW(t.f1, t.f2, 42) FROM t; By default, the value created by a <literal>ROW</> expression is of an anonymous record type. If necessary, it can be cast to a named composite type — either the row type of a table, or a composite type - created with <command>CREATE TYPE AS</>. An explicit cast may be needed + created with <command>CREATE TYPE AS</>. An explicit cast might be needed to avoid ambiguity. For example: <programlisting> CREATE TABLE mytable(f1 int, f2 float, f3 text); @@ -1725,13 +1725,13 @@ SELECT somefunc() OR true; rely on side effects or evaluation order in <literal>WHERE</> and <literal>HAVING</> clauses, since those clauses are extensively reprocessed as part of developing an execution plan. Boolean - expressions (<literal>AND</>/<literal>OR</>/<literal>NOT</> combinations) in those clauses may be reorganized + expressions (<literal>AND</>/<literal>OR</>/<literal>NOT</> combinations) in those clauses can be reorganized in any manner allowed by the laws of Boolean algebra. </para> <para> When it is essential to force evaluation order, a <literal>CASE</> - construct (see <xref linkend="functions-conditional">) may be + construct (see <xref linkend="functions-conditional">) can be used. For example, this is an untrustworthy way of trying to avoid division by zero in a <literal>WHERE</> clause: <programlisting> |