What exactly is SQL for? In what ways?

SQL can be interpreted in two ways: one is Microsoft's SQL Server, a large-scale database system software, which is specially used for mass data storage and management. Another explanation is the abbreviation of structured query language, which is the most widely used database language at present. SQL was developed by IBM and later accepted by many database software companies, becoming the industry standard. Just like the name of SQL, we can use an easy-to-understand query language to process the database and get the data we want from it. For SQL language, there are two components: DML (data manipulation language): they are selection, update, insertion and deletion. As its name suggests, these four commands are used to manipulate the data in the database. DDL (Data Definition Language): DDL is more than DML, and the main commands are CREATE, ALTER and DROP. DDL is mainly used to define or change the structure, data types, links and constraints between tables. They are mainly used when creating tables.