MonetDB准备函数中的语句

Question

I'm trying to create a function that takes the parameters for the column, the table, the limit, and offset. Basically, I want to be able to get a specified number of rows data from a specified table from a specified column.

However, I'm unable to get the following code to work - I get several errors such as:

syntax error, unexpected SELECT, expecting ':' in: "create function get_banana(lim int, off int, tbl varchar(32), col varchar(32)) r"
syntax error, unexpected RETURN in: "return"
syntax error, unexpected END in: "end"

These errors seem kind of meaningless.

My code is as follows:

CREATE FUNCTION GET_BANANA(lim int, off int, tbl varchar(32), col varchar(32)) 
RETURNS TABLE (clm int) 
BEGIN 
    PREPARE SELECT col FROM tbl LIMIT ? OFFSET ?; 
    RETURN EXEC (lim, off); 
END;

I'd appreciate any help :) Thanks!

Answer 1

I see at least two issues

• EXEC needs the identifier that is returned by PREPARE , eg:

   sql>prepare select * from tables; execute prepared statement using: EXEC 2(...) sql>exec 2(); 

• The function parameters tbl and col are string values. You cannot use them as table/column identifiers.

Having said that, I am not even sure if PREPARE can be used inside a function.

Answer 2

不，PREPARE是顶层语句修饰符。