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JDBC Articles
Page 21 of 22
How to change the datatype of a column in an existing table using JDBC API?
You can change the datatype of a column in a table using the ALTER TABLE command.SyntaxALTER TABLE Sales MODIFY COLUMN column_name column_new_datatuypeAssume we have a table named Sales in the database with 7 columns namely ProductName, CustomerName, DispatchDate, DeliveryTime, Price, Location and, ID with description as:+--------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName | varchar(255) | YES | | NULL | | | CustomerName | varchar(255) | YES | | NULL ...
Read MoreHow to get the datatype of a column of a table using JDBC?
You can get the datatype of a column of a table using the getColumnType() method of the ResultSetMetaData class.//Retrieving the ResultSetMetaData object ResultSetMetaData rsmd = rs.getMetaData(); //getting the column type String column_name = rsmd.getColumnTypeName(2);Assume we have a table named employee_data in the database with the description as shown below:+----------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | | Name | varchar(255) ...
Read MoreHow to add a primary key constraint to a column of a table in a database using JDBC API?
You can add a primary key constraint to a column of a table using the ALTER TABLE command.SyntaxALTER TABLE table_name ADD CONSTRAINT MyPrimaryKey PRIMARY KEY (column1, column2...);Assume we have a table named Dispatches in the database with 7 columns namely id, CustomerName, DispatchDate, DeliveryTime, Price and, Location with description as shown below:+--------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName | varchar(255) | YES | | NULL | | | CustomerName | varchar(255) | ...
Read MoreHow to get the size of a column of a table using JDBC?
You can get the size of a column of a table using the getPrecision() method of the ResultSetMetaData class.//Retrieving the ResultSetMetaData object ResultSetMetaData rsmd = rs.getMetaData(); //getting the column type int size_name = rsmd. getPrecision(3);Assume we have a table named employee_data in the database with description as shown below:+----------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | | Name | varchar(255) | YES | ...
Read MoreHow to drop constraint on a column of a table in a database using JDBC API?
You can drop a constraint on a column of a table using the ALTER TABLE command.SyntaxALTER TABLE table_name DROP CONSTRAINT MyUniqueConstraint;Assume we have a table named Dispatches in the database with 7 columns namely id, CustomerName, DispatchDate, DeliveryTime, Price and, Location with description as shown below:+--------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName | varchar(255) | YES | UNI | NULL | | | CustomerName | varchar(255) | YES | | NULL | ...
Read MoreHow to connect to PostgreSQL database using a JDBC program?
PostgreSQL is an open source relational database management system (DBMS) developed by a worldwide team of volunteers. PostgreSQL is not controlled by any corporation or other private entity and the source code is available free of charge.PostgreSQL runs on all major operating systems, including Linux, UNIX (AIX, BSD, HP-UX, SGI IRIX, Mac OS X, Solaris, Tru64), and Windows. It supports text, images, sounds, and video, and includes programming interfaces for C / C++, Java, Perl, Python, Ruby, Tcl and Open Database Connectivity (ODBC).Download the latest version of postgresql- from postgresql-jdbc repository.Add downloaded jar file postgresql-(VERSION).jdbc.jar in your class path.ExampleFollowing JDBC program ...
Read MoreHow to set auto-increment to an existing column in a table using JDBC API?
You can add/set an auto increment constraint to a column in a table using the ALTER TABLE command.SyntaxALTER TABLE table_name ADD id INT PRIMARY KEY AUTO_INCREMENTAssume we have a table named Dispatches in the database with 7 columns namely id, CustomerName, DispatchDate, DeliveryTime, Price and, Location with description as shown below:+--------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName | varchar(255) | YES | UNI | NULL | | | CustomerName | varchar(255) | YES | ...
Read MoreHow to set/insert null values to in to a column of a row using JDBC program?
You can insert null values into a table in SQL in two ways:Directly inserting the value NULL into the desired column as:Insert into SampleTable values (NULL);Using ‘ ’ as nullInsert into SampleTable values (NULL);While inserting data into a table using prepared statement object you can set null values to a column using the setNull() method of the PreparedStatement interface.pstmt.setNull(parameterIndex, sqlType);ExampleAssume we have a table named cricketers_data in the database with the following contents:+------------+------------+---------------+----------------+-------------+ | First_Name | Last_Name | Date_Of_Birth | Place_Of_Birth | Country | +------------+------------+---------------+----------------+-------------+ | Shikhar | Dhawan | 1981-12-05 | ...
Read MoreHow to delete a row from ResultSet object using JDBC?
The deleteRow() method of the ResultSet interface deletes the current row from the current ResultSet object.//Deleting a column from the ResultSet object rs.deleteRow();Assume we have a table named Cricketers_Data with 6 records as shown below:+----+------------+------------+---------------+----------------+-------------+ | ID | First_Name | Last_Name | Year_Of_Birth | Place_Of_Birth | Country | +----+------------+------------+---------------+----------------+-------------+ | 1 | Shikhar | Dhawan | 1981-12-05 | Delhi | India | | 2 | Jonathan | Trott | 1981-04-22 | CapeTown | SouthAfrica | | 3 ...
Read MoreHow to move the result set pointer to required position?
The absolute() method of the ResultSet interface accepts an integer value representing the index of a row and moves the ResultSet pointer of the current ResultSet object to the specified position.Assume we have a table named cricketers_data with 6 records as shown below:+------------+------------+---------------+----------------+-------------+ | First_Name | Last_Name | Date_Of_Birth | Place_Of_Birth | Country | +------------+------------+---------------+----------------+-------------+ | Shikhar | Dhawan | 1981-12-05 | Delhi | India | | Jonathan | Trott | 1981-04-22 | CapeTown | SouthAfrica | | Lumara ...
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