JDBC PreparedStatement忽略'？ '在$$…$$查询块中

Question

I have a PreparedStatement in java. I provide it with query containing '?', something like like

Select .... where date >= ?

This is ok and when i try to set the argument using:

preparedStatement.setObject(1, dateToSet);

it works as expected. However if the query contains $$ ... $$ block it seems the question mark (inside the block) can not be located and when i try to set the argument i receive the following error "The column index is out of range: 1, number of columns: 0"

SELECT * FROM crosstab( $$ Select .... where date >= ? $$ ) AS ct (...);

I also tried to put the ? just after the $$ block (just to make sure), and it was able to locate that one (outside the $$ block). Any ideas how to make the argument placeholder discoverable in the $$ block?

Answer 1

With $$ you have used Dollar-quoted String Constants and ? symbol used for declaring JDBC bind parameters won't be resolved inside a string constant. As per PostgreSQL docs:

While the standard syntax for specifying string constants is usually convenient, it can be difficult to understand when the desired string contains many single quotes or backslashes, since each of those must be doubled. To allow more readable queries in such situations, PostgreSQL provides another way, called “dollar quoting”, to write string constants. A dollar-quoted string constant consists of a dollar sign ($), an optional “tag” of zero or more characters, another dollar sign, an arbitrary sequence of characters that makes up the string content, a dollar sign, the same tag that began this dollar quote, and a dollar sign. For example, here are two different ways to specify the string “Dianne's horse” using dollar quoting:

 $$Dianne's horse$$ $SomeTag$Dianne's horse$SomeTag$ 

Since crosstab() uses a string constant parameter you have to prepare the nested query yourself in Java. This was discussed on the mailing list .