In the 21st century, data is the new oil. Every application, software, device, and equipment has some form of data or information that humans can optimize to make it favorable for them. Businesses now understand the importance of data collection and storage and leveraging them to aid their decision-making process. Databases, i.e., information stored digitally in rows and columns, are fundamental to an IT organization. The handling and maintenance of these databases require a steep learning curve for the best results. Therefore, understanding data manipulation commands (DML Commands) is of utmost importance.
Many Relational Database Management Systems (RDBMS) is used to manage databases, such as MS Access, Oracle, Postgres, MySQL, SQLite, SQL Server, etc. Structure Query Language, also known as SQL, is one of the most popular database languages.
Here, in this article, we’ll look at the Commands of SQL and its syntax to define the different aspects of various Relational Database Management Systems (RDBMS).
The main types of commands present in SQL are:
Take a look at some of the commands of SQL queries in this picture:
Figure: SQL Commands source
DDL is an abbreviation for Data Definition Language. DDL is used to define the schema or the structure of a database. Here are the main DDL commands of SQL with their syntax.
The Create command is used to build new tables, views, and databases in DBMS.
Syntax:
Example:
Executing the Drop command in DDL can remove databases and tables from the RDBMS.
For example:
The Alter command in DDL can change or modify the database structure.
To add a new row in the table,
And to make a change to an existing row in a given database,
DML commands are often part of a more extensive database language, for instance, SQL (Structure Query Language). These DML commands may have a specific syntax to manage data in that language.
DML Commands provide a way to precisely read, update, delete, or merge data. In the beginning, DML commands were part of computer programs only, but with the popularity of SQL, they have now become a part of database management.
Data Manipulation Languages (DML) have two primary classifications: Procedural and Non-procedural programming (declarative programming).
Data Control Language (DCL) provides commands to add more rights and permissions to different aspects of database parameters inside an RDBMS. Grant and Revoke are part of the DCL command in SQL.
The Grant command adds access privileges to a specific database.
The Revoke command provides a way to remove specific permissions from the given user.
Transaction Control Language or TCL represents the transactions in query handling in RDBMS. Commit, Rollback, and SAVEPOINT are the three main TCL commands.
The Commit command saves all the transactions to a specific database.
The rollback command allows you to return or undo any transaction that is not present in the database.
Here is the syntax for SAVEPOINT to specify and set a savepoint in the transaction.
DQL, also known as Data Query Language (DQL), comprises the main commands used to fetch information or data from a database.
SELECT is the primary fundamental query command used with FROM and to give direction to the commands.
For instance:
SELECT writer_name
FROM book_writer
WHERE age > 60;
This query or command will fetch the list of writers who have written books and are aged more than 60.
Here is a short list of all DML commands and their specific functions in the SQL programming language.
The INSERT query command in SQL provides a way to add new rows of information or data inside a specific database of the RDBMS. INSERT can be executed using two syntaxes:
Here ‘column’ represents the table column’s specific names for inserting data in the desired way.
You may avoid the column name and add the values previously defined in the column.
Here is an example of adding five records to the customer database table:
And using the second syntax, you can add the record as that too:
And all the above records will fetch the following result on checking the CUSTOMERS table as follows:
The Update command provides a way to make changes/update or modify the values present in a table’s column.
You can add more conditions using OR or AND operators to make multiple changes using a single query.
Let’s consider the above example.
Now you can update the address of the 5th customer with the following UPDATE Query.
On checking, the customer records will fetch the following result:
And in case you are looking to change the Salary and address of the whole customer database, you can do so with the help of the below-mentioned query:
The Delete command provides a way to delete a single column or multiple columns from a table’s specific row.
You can use a combination of different operators to get more specific or precise results.
And the DELETE query for ID 3 would then be:
Now the database will look something like this:
You can also the use following command to DELETE all customers from a given database:
This will delete all records of the customers from a specific database, respectively.
For example, when a team leader (TL) quits the company, a row has to be inserted into the JOB_ HISTORY table to show when the team leader left, and the value of TL_ID has to be updated against each of his team members in the EMPLOYEES table. To execute this process in a business application, the ‘INSERT’ and ‘UPDATE’ DML commands must be combined into a single transaction.
DML commands have the following applications:
Here are the main differences between DDL and DML commands in RDBMS:
SQL is one of the primary database management languages. Commands of SQL have different types and syntaxes that allow you to manage data precisely and deliver optimum results.
There are five different types of commands within DDL, DML, DCL, TCL, and DQL. Each type has a specific function and role to perform in the programming language.
With both public and private organizations now depending on data to run their operations, data management has become one of the most crucial tools in today’s times. With continued improvisation in technologies, storage, and IT solutions, data manipulation will remain an area of much interest for younger generations.
Software is designed mainly to make life easy. The database is an integral part of the software. Any user interface that collects data from the user is stored in a database. This database is used for further reference. We have all received customer calls if our accounts have not been active for some time. The customer care officials take the data from the database from the column’ last active’ in the table and call the customers.
Finding the right place to learn and become proficient in all these skills and languages is also important. UNext, recognized as one of the Top 10 Data Science Institutes in India, is the right place for you. UNext offers an Integrated Program In Business Analytics for enthusiasts in this field. The course runs for 10 months and is conducted live online. Learners are offered a joint certificate by the Indian Institute of Management, Indore, and UNext.
When executed, the Truncate command in DDL can remove or delete all rows from a specific table and clear or free the table, respectively.
DML is an abbreviation for Data Manipulation Language.
Data Manipulation Language or DML represents a collection of programming languages explicitly used to make changes in the database, such as:
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