Difference Between Execute(), query() and Update() Methods in Java - GeeksforGeeks

05 Oct, 2021
Before getting started, let us have prior knowledge of parameters that makes use of the following three queries parameters, which are as follows:
boolean execute(String SQL): Returns a boolean value of true if a ResultSet object can be retrieved; otherwise, it returns false. Use this method to execute SQL DDL statements or when you need to use truly dynamic SQL.
int executeUpdate(String SQL): Returns the number of rows affected by the execution of the SQL statement. Use this method to execute SQL statements, for which you expect to get a number of rows affected – for example, an INSERT, UPDATE, or DELETE statement.
ResultSet executeQuery(String SQL): Returns a ResultSet object. Use this method when you expect to get a result set, as you would with a SELECT statement.
They are discussed in below listed manner as follows:
execute()execute Query()execute Update()
execute()
execute Query()
execute Update()
Method 1: execute()
Description: The method used for all types of SQL statements, and that is, returns a Boolean value of TRUE or FALSE.
Return type: This method return a Boolean value. TRUE indicates that query returned a Result Set object and FALSE indicate returned an int value or returned nothing.
Usage: This method is use to execute  Both select and non select queries.
Example: All SQL statements.
Illustration: 
Java
// Java Program to Illustrate usage of execute() Method   // Loading the driver using forName() method Class.forName(driver);  // Registering the driver using Drivermanager.getConnection() method Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test",                  "root", "1234");  // Get database connectionstmt = conn.createStatement();  // Use Connection to create a Statement object  // Execute SQL and return boolean value to // indicate whether it contains ResultSetboolean hasResultSet = stmt.execute(sql);  // Condition holds true till there is a single element if (hasResultSet) {      // If there is a ResultSet result set after execution    rs = stmt.getResultSet();    // Get the result set      ResultSetMetaData rsmd = rs.getMetaData();          // ResultSetMetaData is a metadata interface for analyzing result sets    int  columnCount = rsmd.getColumnCount();      // Getting the output ResultSet object    // with help of object of ResultSet     while (rs.next ())     {          for (int i = 0 ; i < columnCount ; i++ )         {            System.out.print(rs.getString(i + 1) + "/t");        }        System.out.print("/n");    }} else {      System.out.println ("The records affected by this SQL statement are"     + stmt.getUpdateCount () + "Article");}
 Method 2: execute Query() 
Description: Now this method execute statements that returns a result set by fetching some data from the database.
Usage: This method is use to execute select query.
Return type: This method returns a Result Set object which contains the result returned by query.
One of it’s example that is widely common: ‘SELECT’
Illustration: 
Java
// Java Program to Illustrate execute Query() Method   // Again first step is to load and register drivers   Class.forName("com.mysql.jdbc.Driver");  Connection  conn = null;conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test",            "root","root");// Using DriverManager to get database connection  Statement  stmt = conn.createStatement();// Use Connection to create a Statement object  // Creating an object of ResultSet class ResultSet rs =stmt.executeQuery("select * from teacher");  // Execute the query statement and save the result// Iterating over elements in above object while (rs.next()) {             // Getting the output the query result           System.out.println(rs.getInt(1) + "/t" +    rs.getString(2));  }
Method 3: execute Update()
Description: This method is used for execution of DML statement(INSERT, UPDATE and DELETE) which is return int value, count of the affected rows.
Usage: This method is use to execute non select query. This method is use to execute select and non select queries.
Return type: An integer value which represent number of rows affected by the query. This will be 0 for statement which are returning nothing.
Example:
DML->INSERT , UPDATE and DELETE
DDL-> CREATE, ALTER
Illustration:    
  Class.forName("com.mysql.jdbc.Driver");
    // Load the database driver
 Connection  conn = null;
 conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test",
        "root","1234");
    // Use DriverManager to get database connection
 Statement  stmt = conn.createStatement();
    // Use Connection to create a Statement object


 return stmt.executeUpdate(sql);
    // Execute the DML statement and return the number of records affected
Now let us finally conclude out the differences in return types as spotted in the above illustrations
execute(): The return type is Boolean, indicating whether ResultSet returnexecuteQuery(): Type method returns a ResultSet, execute returns the results of the query, often used to perform the queryexecuteUpdate(): The return type is int, that the implementation of a number of rows affected after the sql statement, usually used to execute modification statements.
execute(): The return type is Boolean, indicating whether ResultSet return
executeQuery(): Type method returns a ResultSet, execute returns the results of the query, often used to perform the query
executeUpdate(): The return type is int, that the implementation of a number of rows affected after the sql statement, usually used to execute modification statements.
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