What is SQL: Its features and commands

Are you curious about SQL, the domain-specific programming language that manages, manipulates, and retrieves data stored in relational databases? If so, you're not alone. We at keySkillset bring you this awesome simulation based SQL program. You can join the waiting list for our simulation based SQL program via this pre-registration link. Since its inception in the 1970s by Raymond FF Boyce and Donald D. Chamberline at IBM, SQL has become a standardized language of choice for data integration scripts, database administrators, and data analysts.

SQL is a user-friendly language that allows you to retrieve, manipulate, and define data without the need to copy it to other applications. It provides rich transactional support and is capable of handling large records and managing several transactions at once. SQL's high-performance programming capability makes it an excellent tool for managing high-usage, transactional, and heavy workload database systems.

This here is the first blog of the series. Following these we shall be uploading blogs on:

• SQL Server Date Functions 
• SQL Server Math/Numeric Functions 
• SQL Server String Functions 

In this article, we will explore the SQL features, functions, and uses of SQL-the popular choice among data analysts, database administrators, and developers.

SQL Features 

Flexibility and Scalability: SQL provides users with flexibility and scalability for relational database management systems. With SQL, it's easier to create new tables while dropping or deleting previously-created or seldom-used tables.

Comprehensive Application Development Tool: Programmers use SQL to program applications to access a database, making it a comprehensive and effective application development tool. SQL is suitable for every large or small organization, regardless of size.

Rich Transactional Support: SQL's programming capability of handling large records while managing several other transactions is top-notch.

High Performance: SQL offers high-performance programming capabilities for high usage, incredibly transactional, and heavy workload database systems. SQL's programming provides different ways to describe data more analytically.

High Availability: SQL is compatible with other databases such as Microsoft SQL Server, Oracle Database, MS Access, MySQL, SAP Adaptive Server, and more. These RDBMSs support SQL, and it's easier to create application extensions for procedural programming and several other SQL functions that are extra features, hence making SQL a strong tool.

High Security: SQL also has high security as one of its notable features. It's easy to give permissions on views, procedures, and tables. So with SQL, you get optimum security for your data.

SQL's Management Ease: Almost every Relational Database Management System uses Structured Query Language. These commands help users manage large amounts of data from a database efficiently and quickly.

Functions of SQL:

SQL provides a wide range of functions to perform various operations on data. See here how SQL works, where SQL used or how these functions work. In terms of dividing SQL functions, we can categorize them into the following types:

• SQL Server Date Functions 
• SQL Server Math/Numeric Functions 
• SQL Server String Functions  

Different Types of SQL Commands

Transaction Control Language: Transaction Control Language (TCL) is a subset of SQL that is used to manage transactions in a relational database. Transactions are sets of operations that are performed as a single unit of work, and are often used to ensure data consistency and integrity. 

TCL commands can be used to control the transactional behavior of SQL statements, and include the following:

• COMMIT: This command is used to commit a transaction, which means to make all the changes permanent and visible to other users. Once a transaction is committed, it cannot be rolled back.
• ROLLBACK: This command is used to undo the changes made by a transaction and restore the database to its previous state. It is often used when an error occurs during a transaction.
• SAVEPOINT: This command is used to create a savepoint within a transaction, which is a point in time to which the transaction can be rolled back. Savepoints can be used to provide a finer level of control over transactional behavior.

‍TCL is an important feature of SQL because it allows developers to control the behavior of transactions in a database, ensuring that data remains consistent and reliable.

Data Manipulation Language(DML) Commands: Used to manipulate data within a database. These commands allow users to add, update, delete and retrieve data from a database. Examples of DML commands in SQL are given below: 

• SELECT: This command is used to query data from a table. It can be used to retrieve all fields or specific fields from a table.
• INSERT: This command is used to add new records or rows to a table. 
• UPDATE: This command is used to modify existing records in a table. 
• DELETE : This command is used to delete existing records from a table. 

Data Query Language(DQL) Commands: This command is used to fetch the data from the table. It is the most widely used syntax in SQL. 

• SELECT: Used to retrieve data from one or more tables in a database. It can also be used to join multiple tables together. 
• The SELECT statement can include a variety of clauses such as WHERE, GROUPBY, ORDER BY and HAVING to further refine the data being returned

Data Control Language(DCL) Commands:  This command is used to grant or revoke user access to database objects. Now, here are the commands used in this: 

• GRANT :Give permission to access a table /object
• REVOKE :Take away permission to access a table/object

* PUBLIC is all database users

Uses of SQL Commands 

Data Integration Scripts: Database administrators and developers use SQL when writing Data Integration Scripts.

Below are some of the SQL commands commonly used in data integration scripts:

• SELECT: The SELECT statement is used to query data from one or more tables. This command can be used to select specific columns or all columns from a table. It can also be used to filter rows based on specific conditions using the WHERE clause.
• JOIN: The JOIN statement is used to combine data from two or more tables based on a common column. There are several types of JOIN operations, including INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.
• UNION: The UNION statement is used to combine the results of two or more SELECT statements into a single result set. The columns in each SELECT statement must have the same data type and be in the same order.
• INSERT: The INSERT statement is used to insert new rows into a table. The values to be inserted can be specified explicitly or can be the result of a subquery.
• UPDATE: The UPDATE statement is used to modify existing rows in a table. The rows to be updated can be filtered using the WHERE clause.
• DELETE: The DELETE statement is used to delete one or more rows from a table. The rows to be deleted can be filtered using the WHERE clause. 
• CREATE TABLE: The CREATE TABLE statement is used to create a new table with specified columns and data types.
• ALTER TABLE: The ALTER TABLE statement is used to modify the structure of an existing table. This can include adding or removing columns, changing data types, or modifying constraints.
• TRUNCATE TABLE: The TRUNCATE TABLE statement is used to remove all rows from a table without dropping the table itself.
• INDEX: The INDEX statement is used to create an index on one or more columns in a table. This can improve the performance of queries that use those columns in the WHERE or JOIN clauses.

Data Retrieval: SQL users use the programming language to retrieve information. You can use SQL to retrieve the subsets of information in a database for transaction processing and analytics applications.

Here are some commonly used SQL commands for data retrieval:

• SELECT: This is the most common SQL command for retrieving data from a database. It allows you to select one or more columns from one or more tables, and can include filtering, sorting, and grouping of the data. 
• WHERE: The WHERE clause is used to filter the rows retrieved by a SELECT statement. It allows you to specify a condition that must be met for a row to be included in the result set.
• JOIN: The JOIN command is used to combine data from two or more tables based on a common column. It is used when the data you need is spread across multiple tables in a database
• GROUP BY: The GROUP BY clause is used to group rows together based on one or more columns. It is often used with aggregate functions like COUNT, SUM, AVG, MIN, and MAX to perform calculations on the grouped data.
• ORDER BY: The ORDER BY clause is used to sort the rows retrieved by a SELECT statement. It allows you to specify one or more columns to sort by, and whether the sorting should be done in ascending or descending order
• LIMIT: The LIMIT clause is used to limit the number of rows retrieved by a SELECT statement. It allows you to specify an offset (i.e. how many rows to skip) and a maximum number of rows to retrieve.

Analytical Queries: Developers use SQL to deal with analytical queries required in analyzing data and getting much-needed instincts from it.

Here are the SQL commands used for Analytical queries: 

• SELECT: This command is used to retrieve data from one or more tables.
• WHERE: This command is used to filter data based on a condition.
• GROUP BY: This command is used to group data based on one or more columns.
• HAVING: This command is used to filter groups based on a condition.
• ORDER BY: This command is used to sort the data in ascending or descending order based on one or more columns.
• JOIN: This command is used to combine data from two or more tables based on a related column.
• UNION: This command is used to combine the results of two or more SELECT statements into a single result set.
• SUM, AVG, MAX, MIN: These commands are used to perform aggregate functions on a column or group of columns.
• COUNT: This command is used to count the number of rows or non-null values in a column or group of columns.
• RANK, DENSE_RANK: These commands are used to calculate the rank of a row based on a specific column.
• WINDOW functions: These functions are used to perform calculations over a specific set of rows.

Modification of Database Table and Index Structures: SQL is applied in the modification of database tables and modification of the index structures.

Some of the commonly used SQL commands for Modification of Database Table and Index Structures:

• CREATE TABLE: This command is used to create a new table in the database.
• ALTER TABLE: This command is used to modify the structure of an existing table, such as adding, deleting or modifying columns, changing data types or constraints.
• DROP TABLE: This command is used to delete an existing table from the database.
• CREATE INDEX: This command is used to create a new index on a table to improve the performance of queries.
• ALTER INDEX: This command is used to modify an existing index, such as adding or removing columns or changing the index type.
• DROP INDEX: This command is used to delete an existing index from the database.
• TRUNCATE TABLE: This command is used to remove all data from an existing table, while keeping the table structure intact.
• RENAME TABLE: This command is used to rename an existing table in the database.
• ADD CONSTRAINT: This command is used to add a constraint to an existing table, such as a primary key, foreign key or unique constraint.
• ALTER COLUMN: This command is used to modify the data type or size of an existing column in a table.
• DROP COLUMN: This command is used to remove an existing column from a table.

Conclusion 

SQL is a powerful and flexible language that is used to manage relational databases. Its features and benefits include data definition, manipulation, querying, and transaction control, making it a popular choice for developers, database administrators, and data analysts. By using SQL, organizations can efficiently manage large volumes of data, perform complex analytics, and ensure data integrity and consistency. And the best way to master this is via the simulation method at keySkillset.