“Type Mismatch: Cannot Convert from int to ResultSet” [duplicate]

问题:

This question already has an answer here:

• ResultSet is not for INSERT query? Error message: Type mismatch: cannot convert from int to String 1 answer

I am using JCBC API to connect to mySQL server in order to perform some SQL queries (create tables, delete rows, etc.).

However, I receive a "Type Mismatch: Cannot Convert from int to ResultSet" error in the following function:

private static void deleteUnpopularArtists(Statement statement, int min_rank) throws SQLException {      String rank = Integer.toString(min_rank);     ResultSet resultSet = statement.executeUpdate("DELETE FROM record_artist WHERE high_chart_pos < " + rank + ";");  } 

I have tried to use String.valueOf(min_rank); and int rank = min_rank + "";

So my question is, why am I getting this error? What can I do to fix it?

回答1:

executeUpdate returns the number of rows affected in the query. The notion of a ResultSet for a database write operation makes no sense

int rows = statement.executeUpdate      ("DELETE FROM record_artist WHERE high_chart_pos < " + rank + ";"); 

回答2:

 1. ExecuteUpdate returns int - for update, insert and delete operations  where the result is expected to be int ( Number of rows affected ) 

 2. ExecuteQuery returns resultset - useful for query statements (eg. select * from table)  where result type is resultset (data from the table) 

 3. execute returns boolean - when you do not know what function to use for your  query or for unknown dynamic sql use this function. It returns true if result is a resultSet and false if answer is an updateCount 
or no results founds 

Hope this helps!!!

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