Dbms chapter ii
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This document discusses database management system (DBMS) languages including data definition language (DDL), data manipulation language (DML), and storage definition language (SDL). It states that DDL is used by database administrators and designers to define the database schema, DML is used to retrieve and update data, and SDL may be used separately from DDL to define storage structures. It provides examples of DDL commands in SQL like CREATE TABLE and ALTER TABLE.
Dbms chapter ii
- 1. Subject Name Code Credit Hours Database System COMP 219 3 Chapter II
- 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. 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. 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. 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. 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. 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. 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 …..)