Dbms chapter ii

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Dbms chapter ii

  1. 1. Subject Name Code Credit Hours Database System COMP 219 3 Chapter II
  2. 2. Subject Name Code Credit Hours Database System COMP 219 3 DBMS Languages: Types Data Definition Language( DDL) Data Manipulation Language (DML) storage definition language (SDL) storage definition language (SDL) Procedural DML Non-Procedural DML
  3. 3. Subject Name Code Credit Hours Database System COMP 219 3 DBMS Languages – Used by the DBA and database designers to specify the conceptual schema of a database. – In many DBMSs, the DDL is also used to define internal and external schemas (views). – In some DBMSs, separate storage definition language (SDL) and view definition language (VDL) are used to define internal and external schemas. • SDL is typically realized via DBMS commands provided to the DBA and database designers Data Definition Language (DDL):
  4. 4. Subject Name Code Credit Hours Database System COMP 219 3 Data Manipulation Language (DDL): • Data Manipulation Language (DML): – Used to specify database retrievals and updates – DML commands (data sublanguage) can be embedded in a general-purpose programming language (AKA host language), such as COBOL, C, C++, or Java. – Alternatively, stand-alone DML commands can be applied directly (called a query language). DBMS Languages
  5. 5. Subject Name Code Credit Hours Database System COMP 219 3 Data Definition Language (DDL): – Used by the DBA and database designers to specify the conceptual schema of a database. – In many DBMSs, the DDL is also used to define internal and external schemas (views). – In some DBMSs, separate storage definition language (SDL) and view definition language (VDL) are used to define internal and external schemas. • SDL is typically realized via DBMS commands provided to the DBA and database designers
  6. 6. Subject Name Code Credit Hours Database System COMP 219 3 Data Manipulation Language (DML) • Language for accessing and manipulating the data organized by the appropriate data model – DML also known as query language • Two classes of languages – Procedural – user specifies what data is required and how to get those data – Declarative (nonprocedural) – user specifies what data is required without specifying how to get those data • SQL is the most widely used query language
  7. 7. Subject Name Code Credit Hours Database System COMP 219 3 Data Definition Language (DDL) • Specification notation for defining the database schema Example: create table account ( account-number char(10), balance integer) • DDL compiler generates a set of tables stored in a data dictionary • Data dictionary contains metadata (i.e., data about data) – Database schema – Data storage and definition language • Specifies the storage structure and access methods used – Integrity constraints • Domain constraints • Referential integrity (references constraint in SQL) • Assertions – Authorization
  8. 8. Subject Name Code Credit Hours Database System COMP 219 3 DDL statements/commands in SQL • Create table table name(list of attribute & their datatypes); • Create schema schema name authorization author name; • Drop schema schema name cascade/restrict; • Drop table tablename cascade/restrict; • Alter table talename add/drop • Create view view name as (select …..)

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