Class_1_RDBMS

1、UNDERSTANDING RDBMSRDBMSRelational Database Management SystemSpreadsheets vs. DatabasesSpreadsheets vs. Databases Spreadsheets are flat. A spreadsheet has a single table, and common data has to be copied on each row. A relational database can have many tables. A row in a table can reference a row in

2、 a different table, which eliminates duplicated data.DATABASE TABLESDatabaseTable1Table2Table3TABLE STRUCTUREColumn 1(Field 1)Column 2(Field 2)Row 1(Record 1)ValueRow 2(Record 2)DATA VALUE TYPESType NameStorage Occupied/ data valueValid Domain RangeShort Integer2 bytes-35768 to 32767Long Integer4 by

3、tes-2147483648 to 2147483647Float4 bytesAny number from n-45 to n38 Double8 bytesAny number from n-324 to n308Text (string)10 + max. length = bytesAny alphanumeric charactersDate8 bytesJan 1, 100 to Dec. 31 9999LOB (variant)22 + max. length = bytesAny alphanumeric charactersSQL SQL is short for Stru

4、ctured Query Language and is a simple language that provides instructions for building and modifying the structure of databases and for modifying the data stored in the tables. The main commands used to modify and retrieve data Select- Fetches data. Insert- Inserts one or more rows of data. Update-

5、Modifies existing row(s) of data Delete- Deletes rows of data.TWO CLASSES OF SQLTWO CLASSES OF SQLData Manipulation Language (DML) - SQL for retrieving and storing data.Data Manipulation Language (DML) - SQL for retrieving and storing data.Data Design Language (DDL) - SQL for creating, altering and

6、dropping Data Design Language (DDL) - SQL for creating, altering and dropping tables.tables.DATABASES MAKE THESE FOLKS HAPPY .End users and DBMS vendorsDB application programmers e.g. webmastersDatabase administrator (DBA) Designs logical /physical schemas Handles security and authorization Data ava

7、ilability, crash recovery Database tuning as needs evolveIMPLEMENTATION DBA Hardware selection, Working with Network team Tuning the system based on the UAT/QA reports Cloning the base image to text & other types of System Implementing UAT/QA/SANDPRODUCTION DBA Upgrading systems Working with Technical Consultants Audit Checking Pre-Post-Health-Check for changes like patches Performance tu