Groovy Sql从列中获取最大值

Question

I have the following Groovy code to return the max value from the 'id' column from the 'topic' table:

 def rs = sql.executeQuery("select max(id) from topic")

 def maxId = rs.getLong(1)

It doesn't work, I get the following error:

java.sql.SQLException: Invalid column index at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:113) at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:147) at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:209)...

Does any one know what the correct code is? Thanks.

Answer 1

I think it would be easier if you'd use the method firstRow . You can either get the value from the result object by name or by index.

by name:

def row = sql.firstRow("select max(id) as max from topic")
def maxId = row.max

by index:

def row = sql.firstRow("select max(id) from topic")
def maxId = row[0]

Answer 2

Nobody seems to have mentioned that the index in rs.getLong(1) is out of bounds. Getting fields uses a starting index of 0. Binding fields uses a starting index of 1. Why? Historical SQL behaviour.