"date " 参数化查询中的 PostgreSQL 语法错误
PostgreSQL syntax error in parameterized query on "date $1"
尝试参数化我的 SQL 查询（使用 libpq 函数 PQexecParams），我陷入语法错误：
SELECT date
错误是：
ERROR: syntax error at or near ""
解决方案是使用类型转换而不是 date:
SELECT ::date
Prepared statements
可以找到对此的解释 in the chapter Constants of Other Types of the manual:
The ::, CAST(), and function-call syntaxes can also be used to specify
run-time type conversions of arbitrary expressions, as discussed in
Section 4.2.9. To avoid syntactic ambiguity, the type 'string' syntax
can only be used to specify the type of a simple literal constant.
Another restriction on the type 'string' syntax is that it does not
work for array types; use :: or CAST() to specify the type of an array
constant.
大胆强调我的。
准备好的语句的参数实际上不是sting literals而是类型values，所以你不能使用[的形式=16=]。使用其他两种形式之一将值转换为不同的类型，就像您已经发现的那样。
示例：
PREPARE foo AS SELECT ::date;
EXECUTE foo('2005-1-1');
类似于PQexecParams in the libpq C library
文档：
... In the SQL command text, attach an explicit cast to the parameter
symbol to show what data type you will send. For example:
SELECT * FROM mytable WHERE x = ::bigint;
This forces parameter </code> to be treated as <code>bigint, whereas by default
it would be assigned the same type as x. Forcing the parameter type
decision, either this way or by specifying a numeric type OID, is
strongly recommended. ...
alternative，上面引述的，就是把各个数据类型的OIDs用paramTypes[]传递- 如果你真的需要演员表。在大多数情况下，让 Postgres 从查询上下文中派生数据类型应该可以正常工作。
paramTypes[]
Specifies, by OID, the data types to be assigned to the parameter
symbols. If paramTypes is NULL, or any particular element in the array
is zero, the server infers a data type for the parameter symbol in the
same way it would do for an untyped literal string.
可以从系统目录中获取数据类型的OID pg_type:
SELECT oid FROM pg_type WHERE typname = 'date';
您必须使用正确的内部类型名称。例如：int4 for integer.
或者方便地转换为 regtype:
SELECT 'date'::regtype::oid;
这更加灵活，因为也接受类型名称的已知别名。例如：int4、int 或 integer for integer.
尝试参数化我的 SQL 查询（使用 libpq 函数 PQexecParams），我陷入语法错误：
SELECT date
错误是：
ERROR: syntax error at or near ""
解决方案是使用类型转换而不是 date:
SELECT ::date
Prepared statements
可以找到对此的解释 in the chapter Constants of Other Types of the manual:
The
::,CAST(), and function-call syntaxes can also be used to specify run-time type conversions of arbitrary expressions, as discussed in Section 4.2.9. To avoid syntactic ambiguity, thetype 'string'syntax can only be used to specify the type of a simple literal constant. Another restriction on the type'string' syntaxis that it does not work for array types; use::orCAST()to specify the type of an array constant.
大胆强调我的。
准备好的语句的参数实际上不是sting literals而是类型values，所以你不能使用[的形式=16=]。使用其他两种形式之一将值转换为不同的类型，就像您已经发现的那样。
示例：
PREPARE foo AS SELECT ::date;
EXECUTE foo('2005-1-1');
类似于PQexecParams in the libpq C library
文档：
... In the SQL command text, attach an explicit cast to the parameter symbol to show what data type you will send. For example:
SELECT * FROM mytable WHERE x = ::bigint;This forces parameter
</code> to be treated as <code>bigint, whereas by default it would be assigned the same type as x. Forcing the parameter type decision, either this way or by specifying a numeric type OID, is strongly recommended. ...
alternative，上面引述的，就是把各个数据类型的OIDs用paramTypes[]传递- 如果你真的需要演员表。在大多数情况下，让 Postgres 从查询上下文中派生数据类型应该可以正常工作。
paramTypes[]Specifies, by OID, the data types to be assigned to the parameter symbols. If
paramTypesisNULL, or any particular element in the array is zero, the server infers a data type for the parameter symbol in the same way it would do for an untyped literal string.
可以从系统目录中获取数据类型的OID pg_type:
SELECT oid FROM pg_type WHERE typname = 'date';
您必须使用正确的内部类型名称。例如：int4 for integer.
或者方便地转换为 regtype:
SELECT 'date'::regtype::oid;
这更加灵活，因为也接受类型名称的已知别名。例如：int4、int 或 integer for integer.