Before Insert trigger in Derby DB - mysql

Question

I am building a javafx project using netbeans and am using derby database for that.
I have two tables, BOOK and ISSUE.
I want to create a BEFORE INSERT trigger ON ISSUE table which checks for the value of a boolean field called "available" in the BOOK table.
A button called BookIssue when pressed, should check the following trigger.
If the value of "available" is false, a warning message should pop up, else the insert operation must be executed.
I am not able to get the trigger command right.
String trigger = "CREATE TRIGGER toIssue NO CASCADE BEFORE INSERT ON ISSUE"
+ " FOR EACH ROW"
+ " BEGIN"
+ " SELECT isAvail from BOOK WHERE id = '"+ bookId + "'"
+ " IF isAvail = false"
+ " THEN RAISE_APPLICATION_ERROR(-20001,'Books Out of stock')"
+ " END IF"
+ " END";
databasehandler.execQuery(trigger);
I am getting following exception in my log:
Exception at execQuery:dataHandlerSyntax error: Encountered "BEGIN" at line 1, column 71.
Could someone help me with this! I couldn't find any other place which had a similar issue with derby.

Answer 1

I think you want: ExecuteNonQuery().
In addition, this line is suspect:
SELECT isAvail from BOOK WHERE id = '"+ bookId + "'"
The trigger body should look more like this:
DECLARE v_avail boolean;
SELECT b.isAvail INTO v_avail
FROM BOOK b
WHERE b.id = NEW.ID;
IF NOT v_isAvail THEN
RAISE_APPLICATION_ERROR(-20001,'Books Out of stock')"
END IF;