使用JDBC驱动程序从Java声明和使用t-sql变量

Question

I'm trying to run this sql script from a java client on a sql server.

DECLARE @CON_NAME VARCHAR(100);
DECLARE @COMMAND VARCHAR(200);

SELECT @CON_NAME=NAME FROM sys.key_constraints WHERE  [type] = 'PK' AND [parent_object_id] = Object_id('dbo.MY_TABLE');
SELECT @COMMAND=CONCAT('ALTER TABLE MY_TABLE DROP CONSTRAINT ', @CON_NAME);
SELECT @COMMAND;
EXEC (@COMMAND);

What the java client does is run the script line by line.

I'm getting the exception below:

com.microsoft.sqlserver.jdbc.SQLServerException: Must declare the scalar variable "@CON_NAME".

How can I solve this issue?

Answer 1

Instead of running the script line by line, send the entire script as one statement.

Running each line separately, means you're running multiple scripts, like if you had put each line in a separate .sql file.

DECLARE 'd variables are local to the script, so running the lines individually makes no sense.

Answer 2

Must declare the scalar variable "@CON_NAME"

Though guess but I think you haven't wrapped your posted SQL code in a procedure rather you are just running/calling them line by line from your java application code like a normal sql query and so the error. Cause by the time it reaches to the line where the variable is getting used that variable declaration is no more present in that scope.

You should consider put this code inside a stored procedure and call that procedure from your code behind rather.