Is Java a data definition language?

What is a data definition language?

Data definition languages (DDL) are computer languages used to create and modify structures of database objects in a database. Database objects examples include views, schemas, indexes, and tables. For instance, a data definition language can modify, add or remove tables in a database. 

Data definition languages are also called data description languages because they describe the fields and the records in a database table. Data definition languages used in database applications are taken as a subset of SQL – Structured Query Language. Nevertheless, DDLs may also define other data types like XML.

The modern database industry incorporates DDL into languages that describe data, though mostly considered a subset of SQL. SQL uses imperative verbs with standard English-like sentences to implement data modifications. DDL doesn’t show up as a separate language in an SQL database but defines changes in the database schema. 

Data definition languages have predefined syntax for data description. For instance, to create a new table using SQL syntax, use the CREATE command, followed by table name parameters and column definitions. Also, the DDL can define the name of each column alongside associated data types. 

After creating the table, you can modify it using the ALTER command. If you no longer need the table, use the drop command to delete the table. 

Other statements include: 

• ALTER – modifies the existing Database
• TRUNCATE – quickly removes all records from a table 
• RENAME – used alongside the ALTER TABLE statement to modify the name of an object (table, column, etc.) 
• COMMENT – used to add a single line, multi-line, and in-line comments.

DDL is a subset of SQL; therefore, it doesn’t include all possible SQL commands. For instance, commands such as INSERT and SELECT are regarded as part of the Data Manipulation Language (DML). By contrast, access commands like EXECUTE and CONNECT are part of the Data Control Language (DCL). The DDL, DML, and DCL languages feature most of the commands supported by SQL.

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What is the use of a data definition language?

The primary function of a data definition language is to create, manipulate and modify structures within a database – columns, functions, tables, views, schemas, etc. Additionally, they perform account level and session operations like setting parameters, initiating transactions, and initializing variables. 

The typical operations in a DDL include Create a Database, Rename a Database, Use Database, Drop Database, Create a Table, Rename Table, and Add a Column to exiting the table. Besides, you can also perform operations like adding multiple columns to an existing Table, Modifying a current column, Truncate a Table, Rename a Column, Drop a Column, and Drop a Table. 

A DDL typically explains the fields of a database table. 

Programmers and data scientists can use a DDL at various levels. For instance, at a higher level, programmers can utilize a DDL’s ability to change structures and alter a database structure, including tables within a database. Also, at specific levels, SQL statements starting with DROP, CREATE, ALTER, or TRUNCATE is data definition language – for example, DROP INDEX, CREATE DATABASE, ALTER TABLE, etc.

For instance, an ALTER statement changes the properties of an object inside a relational database management system (RDBMS). However, you cannot alter all types of objects, depending on RDBMS in use. This also applies to the DROP statement; however, most support dropping tables, databases, and users. 

However, TRUNCATE TABLE is unique because its effects mimic a DELETE FROM [TABLE];. But it (TRUNCATE) operates outside the transaction system. Besides, it’s implementation is almost always internally as a DROP TABLE + CREATE TABLE. Here, the schema is preserved while all rows are gone. Note that the TRUNCATE statement is much faster than the DELETE; so, if you want to delete all the content from a table, quicker the Truncate statements might be helpful. 

What are the examples of a data definition language?

By now, you know that data definition languages are used to create and modify data – for instance, its various commands can be used to modify, add, remove objects in a table. There are many examples of using a DDL, which depend on the commands at hand. 

Important Data Definition Language Commands

ALTER 

This DDL command modifies an account-level/ database object metadata or the parameter for a session. Its syntax would appear as:

ALTER ACCOUNT SET 

ALTER SESSION SET 

ALTER  <actionsNote,  actions  is specific to object types. 

CREATE

This command is used to create new specified object type. For instance: 

CREATE [ OR REPLACE ]  [ IF NOT EXISTS ] 

  [  ]  [  ]  [ COMMENT = ‘‘ ]The object_type_params  and object_type_properties are specific to the object type. COMMENTThis command can be used to either add a new comment or overwrite an existing statement for an object. Programmers can add comments to all things and individual table columns. Syntax:COMMENT [IF EXISTS] ON   IS ‘‘;

COMMENT [IF EXISTS] ON COLUMN 

. IS ”;DROP It is used to remove a specified object from the system.Syntax:DROP  [ IF EXISTS ]   [ CASCADE | RESTRICT ]DESCRIBE Its explains the details for specified objects. Its syntax:DESC[RIBE]  SHOW It shows all existing objects for a specified object category. Its output includes data for the object – Common properties like name and creation timestamp and Object-specific properties.USE It specifies the role, schema, or Database to use for the current session. All the above commands take an object type and identifier while the remaining parameters and options, which are object-specific, can be specified for the command. 

What are the 3 SQL data definition languages? SQL is used for the retrieval and management of data in a relational database. This database language is the standard language for database management. All the RDBMS systems such as MySQL, MS Access, Postgres, Oracle, Sybase, and SQL Server use SQL as their standard database language. SQL program uses various commands for different operations:Data Definition Language StatementsData Definition Language allows coders to define the database structure or schema. The tasks you can perform here include:

• Create, alter, and drop schema objects
• Analyze information on a table, index, or cluster
• Grant and revoke privileges and roles
• Add comments to the data dictionary
• Establish auditing options

Commands such as CREATE, ALTER, and DROP require exclusive access to the specified object. For instance, an ALTER TABLE statement will fail if another user has an open transaction on that particular table.The GRANT, ANALYSE, REVOKE, AUDIT, and COMMENT commands do not need exclusive access to a specified object. That means you can analyze a table while other users are updating the same table. Oracle Database commits the current transaction before and after every data definition language statement. Many DDL statements can cause Oracle Database to recompile or reauthorize schema objects. Data Manipulation Language StatementsA Data Manipulation Language (DML) lets you modify the database instance by inserting, changing, and deleting the data. A DML is responsible for performing all data modification in a database. It comes with three basic constructs that allow the database program and user to enter data and information.

• INSERT – it is a SQL query used to insert data into a row of a table. 
• UPDATE – it used to modify a value in the column of a table
• DELETE – the command removes one or more rows from a table 

Data Control Language (DCL)DCL includes commands such as GRANT and REVOKE. These are helpful commands to give “rights & permissions.” 

• Grant – it gives users access to a database 
• Revoke – useful in backing permission from the user.

Data definition language example.  The primary example of a data definition language is based on the examples of its commands. Ideally, with these commands, you create and manipulate data structures within any database. CREATE has the primary function of this aspect is to develop new tables. Good thing; it comes with a predefined syntax, making it very easy to create components in a relational DBMS (database management system). There are many implementations to extend the syntax of the command to build additional elements – for instance, indexes. ALTER is a command that modifies an existing database object. While using this command, you can add additional columns as well as drop the existing ones. Moreover, you can also change data types in the column. DROP, on the other hand, allows you to delete databases, views, or Tables. Ideally, it lets you remove any component from the relational database management system. Many systems allow DROP to occur inside a transaction, and it can be rolled back. 

Once the DROP statement is executed, that object won’t be available again.The DROP statement is different from the DELETE and TRUNCATE statements – they do not remove the table itself. For instance, a DELETE statement might delete all or some data from a table and leaves the table in the Database. By contrast, a DROP statement removes the entire table from the Database.The TRUNCATE command allows users to remove table content, but it retains the Table structure, i.e., it removes all records from a table. So, while using the truncate statement, you won’t be able to remove the data partially. Besides, the truncate command removes every allocated space.  Keep in mind that within the SQL are statements that define the referential integrity relationships. These are usually implemented as primary key and foreign key tags. They include CREATE TABLE or ALTER TABLE sentences.

Data definition language and data manipulation languageTables are the primary storage point for data in Relational Database Management System. The tables ideally area a collection of related data – data is stored in columns and rows. This data storage method is very efficient, i.e., it makes it easy to use the data when the need arises. Manipulating or retrieving that data requires Structured Query Language (SQL), which comes with standard commands interacting with the RDBMS. The Data Definition Language (DDL) defines a database schema, tables, etc. By contrast, the Data Manipulation Language (DML) manipulates the data that already exists in the Database – for instance, delete, insert and update statements. How do the two compare?Data Definition Language (DDL) Manipulation Language (DML)  Its statements create Databases, constraints, users, schema, tables, etc. DML statement insert, update or delete records in a database  The drop command deletes the table or table objects – it removes data and table definition. So, you need to exercise care while using this command.   The delete command deletes the records from the table.   The CREATE command creates tables or table views. Besides, it can make other objects such as triggers, indexes, and procedures. The INSERT commands insert data into the database tables.   Commands are instantly committed. Commands executed according to rules of transaction.  The Alter command modifies the existing table structure or objects within the Database. The update statement updates the existing information within the tables.   There is no further classification.  It is classified further into two procedural and non-procedural DML.  The command statement operates in the entire table  

The command statements work only on rows   There is no WHERE clause on statements to filter the data.  All statements use the WHERE clause to filter data.   Changes made by the DDL statements cant be rolled back. That means you don’t need to run ROLLBACK or COMMIT.  The ROLLBACK and COMMIT commands must be run to confirm changes.   Data definition language commandsData description and manipulation are a necessity for people dealing with data. Incorporating these capabilities into programming languages makes it extremely easy to handle a wide range of data, no matter their size. A data definition language is simply a syntax used for creating and modifying objects within a database. With a data definition language, you can manipulate various aspects of a database to develop desirable results. The ease of use and efficiency remains the common issues across multiple programming languages for data definition. DDL statements are just like other computer programming languages that define data structures, especially database schemas. While using the data definition language, you must use commands such as DROP, ALTER, and CREATE. Most data description languages use a declarative syntax to define columns and data types. By contrast, Structured Query Language (SQL) uses a collection of imperative verbs that modify the Database’s schema in various ways – changing, adding, or deleting definitions of tables or other elements. The SQL statement can be conjoined with other statements. This makes data definition language, not a different language. The commands include:CREATE TABLE statement: This is the most commonly used command. It uses a comma to separate aspects. 

• Primary key definition: PRIMARY KEY ( [comma separated column list] )
• Column definition: [column name] [data type] {NULL | NOT NULL} {column options}
• Constraints: {CONSTRAINT} [constraint definition]

DROP statement: use this statement to destroy any existing database and all components. However, its functioning depends on the type of RDBMS.ALTER statement: use this command if you want to modify an existing database object. It changes the properties of an object within a relational database. TRUNCATE statement: this command deletes all data from a table; use it if you need faster action. 

Data definition language statements in SQLSQL statements fall under two main classes, i.e., data definition language (DDL) and data manipulation language (DML). While they sound simple, both classes feature dozens of statements that users can manipulate data to their liking. Again, each statement is far more complex than it may appear. Nonetheless, in most cases, the statements are presented in an easy-to-understand manner. The execution of data definition language statements always results in immediate response, i.e., it takes effect immediately. While creating a table, you’ll most frequently use data types that character strings, which may be referred to as VARCHAR or CHAR. This covers variable or fixed-length strings, numeric types like NUMBER or INTEGER (usually specify a precision), and DATE or related types. The syntax for the data types usually varies across the different systems. So, you must consult the software documentation to be sure which one you are using. While altering the table, use the modified table statement – it may be used to specify both primary and foreign key constraints. Moreover, it can be used to perform other modifications to the table structure. The create table statement also allows you to specify the key constraints – specify the constraint’s name.  

Typical advice using a convention that helps get hold of everything – for instance, tablename_pk (e.g., Customers_pk). This way, you can remember what you did later. An attribute list always contains one or more attributes that form this PK; suppose more than one attribute separates them by a comma.The foreign key constraint is a bit complex since you have to specify both the FK attributes in the child table and the PK attributes that link to them in the parent table. Always separate foreign key definitions for each relationship in which this table is the child. Messing things up will require you to start over again. However, you can drop everything with a drop statement. Conclusion Java is a very simple yet high-performance object-oriented programming language. Besides, this language is distributed, multi-threaded interpreted, and portable, mainly intended for building object-oriented, network-based software for Internet applications. The data types in Java specify the size and type of values that an identifier can store. 

Remember, Java is rich in data types, which allows you to choose the appropriate style for your needs. Besides, there are lots of data manipulation commands. It’s accurate; empty tables are not helpful. Plus, even if you add data, you need some way to manipulate the data to make it worthwhile. SQL data manipulation commands can help you read data in the table – ideally, you can create, update, and remove existing data. Good thing; you can use SQL with Java to make the entire process easy. But what you’ll be doing is simply using the Java Database Connectivity (JDBC) to allow Java to connect to SQL databases. But persistence layers like Hibernate exist, and you can use them to store and retrieve data in a database using Java.SQL performs operations on the records stored in the database; if you want to update records, delete records, create and modify tables, views, etc., SQL can do it all. SQL isn’t a database system; instead, it is a query language. 

So, if you want to perform SQL language queries on the stored data in the Database, install any database management system in your systems first – for example, Oracle, MySQL, MongoDB, PostgreSQL, SQL Server, or DB2. DDL is a distinctive set of SQL commands that allows you to manipulate the Database structure, and DDL offers a way to view specific SQL commands. You can use Statement in JDBC. If you want to execute a static SQL statement and return the results it produces, use java.sql.Statement. This statement is efficient for all DDL commands in Java JDBC – CREATE, DROP, ALTER, and TRUNCATE. 

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