Relational and non-relational databases

What is SQL

SQL refers to the Structured Query language, which is an ANSI (American National Standards Institute) standard computer language, It is primarily used to access and manipulate database systems. Some relational databases require semicolons at the end of each SQL command, such as MySQL (if you do not use semicolons at the end of the command), if the relational database you are using is MS SQL Server or SQL Server, You do not need to use semicolons at the end of each SQL command.

Rdbms

RDBMS refers to relational database management system, RDBMS is the foundation of SQL, also is the basis of many now relational database, RDBMS data is stored in the database object called table, the table is a collection of related data items, composed of rows and columns, which is also the typical characteristics of relational data.

DML and DDL

SQL is divided into two parts: Data manipulation Language (DML) and data definition language (DDL).

DML is primarily used to perform queries, updates, insertions, and deletions of syntax. The main DML statements for SQL are:

1) SELECT----FETCH data from the database table

2) Update----updating data for database tables

3) Delete----Remove data from the database table

4) INSERT INTO----inserts data into the data table

DDL primarily creates and deletes databases or tables, can also define indexes (keys), specify links between tables, and impose constraints between tables. The main DDL statements are:

1) CREATE DATABASE----new databases

2) ALTER DATABASE----Modify databases

3) CREATE TABLE----new tables

4) ALTER TABLE----Change database table

5) DROP TABLE----Delete tables

6) Drop DATABASE----Delete databases

7) CREATE INDEX----indexed (search key)

8) DROP INDEX----Delete indexes

The Mainstream relational database

Microsoft SQL Server, IBM DB2, Oracle, MySQL, Microsoft Access, SYBASE,IBM Informix.

Nosql

NoSQL, refers to a non-relational database. From the above narrative, you can see that the tables in the relational database are stored in a formatted data structure, and the composition of each tuple field is the same, even though not all of the fields are required for each tuple, but the database assigns all the fields to each tuple, which makes it easier to connect the table to the table, But from another point of view it is also a factor in relational database performance bottlenecks. Instead of relational databases stored in key-value pairs, its structure is not fixed, each tuple can have a different field, each tuple can increase or decrease some of its own key-value pairs as needed, so that the fixed structure will not be limited, you can reduce the cost of some time and space.

NoSQL has those

Mangodb,membase,hypertale,apache Cassandra,bigtable,couchdb,dynamodb,simpledb, HBase (HadoopDatabase), Redis

Relational and non-relational databases