Originally based upon relational algebra and tuple relational calculus, SQL consists of many types of statements, which may be informally classed as sublanguages, commonly: a data query language (DQL), a data definition language (DDL), a data control language (DCL), and a data manipulation language (DML). Secondly, it eliminates the need to specify how to reach a record, e.g. Firstly, it introduced the concept of accessing many records with one single command.
SQL offers two main advantages over older read–write APIs such as ISAM or VSAM. data incorporating relations among entities and variables. It is particularly useful in handling structured data, i.e. Structured Query Language ( SQL) ( / ˌ ɛ s ˌ k juː ˈ ɛ l/ ( listen) S-Q-L, sometimes / ˈ s iː k w əl/ "sequel" for historical reasons), is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS).
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