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

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:

1. execute()
2. execute Query()
3. 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 connection
stmt = conn.createStatement();

// Use Connection to create a Statement object

// Execute SQL and return boolean value to
// indicate whether it contains ResultSet
boolean 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

1. execute(): The return type is Boolean, indicating whether ResultSet return
2. executeQuery(): Type method returns a ResultSet, execute returns the results of the query, often used to perform the query
3. 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.