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What is SQL?
It is known as Structured Query language and is used in programming as well as designing for management of data that is being held in RDBMS or also stream processing in RDSMS. It is mainly used for handling structured data that is data incorporating relations among variables and entities.
It gives two major advantages over the older used API like ISAM or VSAM for read-write operations that is it made the concept of accessing the thousand of records in a single command and secondly also eliminates the need of specifying how to access the record that is with or without the index.
SQL is based or formed on relational algebra and tuple relational calculus.
It consists of many types of statement, which can be classified as sublanguages:
- DDL- Data Definition Language.
- DML- Data Manipulation Language.
- DCL- Data Control Language.
- DQL- Data Query Language.
- TCL – Transaction Control Language.
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DDL- Data Definition Language:
It is a syntax for defining the data structures in database schemas. It is used to create and modify database objects like tables users and indexes. Common DDL operations are:
DML- Data Manipulation Language:
It is a syntax or language that is used for inserting, deleting and modifying data in a database. common DML operations are:
DCL- Data Control Language:
It is a syntax that is used to control access to data stored in a database.it includes only two commands that are:
- Grant-it allows specific users to perform specific tasks only.
- Revoke-it is used to remove the user accessibility to a database object.
Restriction in DCL
- In oracle use of DCL commands causes an implicit commit, therefore, we will no be able to roll back the command.
- PostgreSQL using DCL commands is transactional and they can be rolled back as well.
- SQLite does not support any DCL commands.
DQL- Data Query Language:
it is a syntax or language used to make queries in databases it tries or attempts to give factual answers to factual questions.
TCL – Transaction Control Language:
These commands are used to manage the transactions in the database. these commands are used to manage the changes that are being made by the use of the DML statements.
Advantages of the SQL:
- High speed - By using SQL queries one can easily, quickly and efficiently access a large amount of data from the database.
- No coding needed - It is very easy to manage the database by SQL as it does not require any programming knowledge either use a very substantial amount of programming to manage the database system.
- Well defined standards - Only those standards are being used which are defined by the ISO and ANSI.
- Portability - SQL gives us so many options that it can be used on various platforms like a laptop, pc or even in some smartphones.
- Interactive language - It can be said that SQL is the domain language that is being used by database for communication and it is also being used to receive answers to the complex queries thrown at it.
- Multiple data view - By using SQL the users have many more different options of making different views of the database structures.
Disadvantages of the SQL:
- Interfaces – It is true that no complex coding is involved in the SQL but still the process interfacing the structure of data is complex.
- Complex interface – SQL does have a complex interface that makes it very difficult for certain users to access and modify it as per their needs.
- Implementation - Although SQL databases conform to ANSI & ISO standards, some databases go for proprietary extensions to standard SQL to ensure vendor lock-in.
- Only partial control – the developers who are using the SQL always do not have full control over the database as a result of some business or organization rules.
- Expense – SQL operations are expensive hence it makes it difficult for bringing the vendor-in.
- It is platform dependent language.
- It is a command-based language.
- It occupies some more space that is extra memory allocation for each record that is entered in the table.
So, when combined the what has been listed above it allows us to frame the important information that within our database using meaningful representations. there are many people who start learning different languages like python, java, c or c++ and they think SQL learning like a deviation from the goal. Yes, it is not an object-oriented language, but it is a declarative language. So we have to keep in mind that SQL is very essential language as it is being used in various applications and web applications.so, whether we are running the online site or maintaining the app there comes a point where we have to store some kind of information and that’s where SQL comes into the play.