PostgreSQL准备好的语句不起作用

Question

当我输入以下准备好的陈述时：

PREPARE pstmt AS SELECT substring(indhold from $1 for $2) FROM mediefil WHERE id = $3

输入以下命令执行：

EXECUTE pstmt (1, 524288, '{01428c12-6c7c-148b-ca35-9d344dfbf8e8}')

我收到一个奇怪的错误：

2013-11-25 18:47:37 CET ERROR:  invalid escape string
2013-11-25 18:47:37 CET HINT:  Escape string must be empty or one character.
2013-11-25 18:47:37 CET CONTEXT:  SQL function "substring" statement 1
2013-11-25 18:47:37 CET STATEMENT:  EXECUTE pstmt (1, 524288, '{01428c12-6c7c-148b-ca35-9d344dfbf8e8}')

为什么会这样？我怎样才能使准备好的声明有效？

Answer 1

尝试投射参数：

PREPARE pstmt(int, int, uuid) AS
SELECT substring(indhold from $1 for $2) FROM mediefil WHERE id = $3