SQL or Structured Query Language is a programming language used to manage to store, updating, and retrieving data in relational databases. SQL is not a standalone programming language, but it allows the developers to create some procedural extensions in combination with other programming languages, which enables it to function like a matured programming language.
SQL was developed as a query language in the 1970s for the then existing database management systems. First known as SEQUEL, it was later renamed to the short form of “SQL” for the trade-marking purposes. SQL also holds the fame of being the first language adopted by ANSI back in 1986 itself and also got ISO by 1987. Many newer versions of SQL were created since its inception with the addition of many new features.
SQL was primarily launched as a standardized way to manage and query data from a relational database. Over the years, it had become wider and complicated, making it much of a developer tool than that of the end user. Even with may standardizations, most of the major leading SQL implementations differ from one another that it becomes very hard to port it to another DBMS without a significant amount of modifications. This accounts to the complexity and oversize of the SQL standard and it also still lacks specifications in different key implementation areas.
In any case; however, SQL remains as one of the most widely used DBMS languages even though there are many competitors. Justifying its initial objective, SQL is still being used the most for the database-oriented development projects. There are four sublanguages under SQL, which are DDL, DML, DCL, and TCL.
Principal sublanguages of SEO
- Data Definition Language
Data Definition Language (DDL) defines different data structures in the given database. DDL SQL codes will let you create, edit, or delete the database objects individually. The allowed object types in DDL will be based on the particular database management system used. IT primarily includes the databases, tables, users, and some primary items like indexes and roles, etc.
- Data Manipulation Language
Data Manipulation Language (DML) has primarily used data querying and also to change the data in a relational database. Various statements in it will let the users insert, select, update, and erase data from the corresponding tables. All the DML statements are declarative in nature, so sometimes the select statements are not counted as DML as they don’t change the existing state of data.
- Data Control Language
Data Control Language (DCL) commands are meant to control the database accesses. These statements run with access privileges to allow and revoke the privileges to apply different DML and DDL commands to a particular set of objects in the database.
- Transaction Control Language
Transaction Control Language (TCL) is to control transaction processing in the database. The typical TCL statements are meant to:
- Apply some changes initiated by a transaction
- Undo or rollback them, and
- To divide transactions into smaller parts etc.
The programmers should know that SQL instates declarative programming standards. Each SQL statement declares the required action, and it’s the DBMS which has to decide how to plan the primary operations and execute the actions. As RemoteDBA.com specifies, it is important for a developer to know how the DBMS analyzes the SQL statements and execute it to use SQL efficiently in database management.
For those who are new to handling SQL, here we will discuss frequently asked questions on it and the expert answers for them.
How to retrieve data from a relational database with SQL? Or which command is used to retrieve data from DB?
‘SELECT’ is the SQL command used to retrieve specific information from the database.
How to create a new database or table using SQL?
Programmers may use the commands as ‘CREATE DATABASE’ or ‘CREATE TABLE’ for the respective tasks. All these SQL commands put forth a very flexible syntax, which allows the users to create customized tables and DBs to suit their business needs.
How to add more data to the database using SQL?
‘INSERT’ is the SQL command to add more records into a structured database table.
How to delete unwanted database tables?
More so often, programmers may need to remove unwanted information also from a relational database to avoid clutter and enhance its performance. SQL offers a very flexible command as ‘DELETE’ to use for removing parts or whole data stored in tables.
What is referred to as NULL Value?
A NULL value is given to an unknown data. NULL is treated in a unique way by the databases based on its type of operation.
How to combine data from different database tables?
The join statements of SQL will let the programmers combine data from multiple tables to show as query results. However, this is another big topic for discussion, which we will discuss in the forthcoming articles.
Is it okay to join a specific table to itself?
It is possible to self-join a table to itself, which will further simplify the nested SQL queries when the outer and inner queries will refer to the same table. Such joins will allow the users to retrieve all related info on the same table.
How to summarize data within a table?
SQL has some mighty commands to aggregate the summarization of big volume of data. SUM command of SQL can be used within the SELECT statement, which returns the desired value series. SQL also provides COUNT function which helps retrieve the number of records in any table which meets the criteria. MAX() command may return a large value among the data and on the other hand MIN() will return the smallest.
How to do the grouping of summarized data?
You can use some basic queries for data retrieval from the relational database. However, when it comes to business intelligence with the need for data visualization, this may not be enough. However, SQL also provides some solutions for the users to view the database query results in a customized manner way over specific row-level attributes by using the GROUP BY clauses to aggregate the data.
SQL database management is not difficult if you get a good grip on many such commands and the practical usages of it.