QSpiders - SQL (Data Base)
- 2. Data is a useful information. Which helps to make a decision. Set of information of any entity is known as data. Example: Employee information.(Name,job,sal etc…) Product information Sales information • What is Data?
- 3. •What is Database ? Place where you store data A database is a systematic collection of data. Databases support storage and manipulation of data. Databases make data management easy. Ex: An online telephone directory. Electricity service provider Facebook.
- 4. • What is a Database Management System (DBMS)? Database Management System (DBMS) is a collection of programs which enables its users to access database, manipulate data, reporting / representation of data . Data base combined with management system services is known as DBMS.
- 5. Oracle 2, Oracle 3, Oracle 4, Oracle 5, Oracle 6, Oracle 7, Oracle 8i, Oracle 9i, Oracle 10g, Oracle 11g and the latest to hit the market is Oracle 12c. here ‘i’ stands for Internet, ‘g’ stands for Grid / Grid computing and C for Cloud Computing . • Here the services are. Entering new data Updating old data with new data Deleting unwanted data Authenticating the users Providing security • The s/w which is widely used today is Oracle. • The different versions of Oracle starting from the earliest to the latest are –
- 6. •What is Relational Database? It is the collection of relations or two dimensional tables Dr E.F Codd proposed the relational model for database system in 1969 Relational Model Consists of following Collections of Objects or Relations Set of Operators to act on the relations Data integrity for accuracy and consistency. ( Data integrity is the one which contains correct data in the database) To restrict storing wrong data in database we use data integrity. To Preserve data integrity we have two types 1.DataType: 2.Constraints: Data Type is a type of data which you store in each column.
- 7. A constraint is a condition which restricts the invalid data in the table. A constraint can be provided for a column of a table. •Constraints A constraint is a condition which restricts the invalid data in the table. A constraint can be provided for a column of a table. •Types of Constraints NOT NULL UNIQUE Primary Key Foreign Key Check
- 8. • Null NULL is nothing, it is neither zero nor blank space It will not occupy any space in the memory Two NULLS are never same in Oracle NULL represents unknown value Any arithmetic operation we perform on NULL will result in NULL itself. For ex, 100000 + NULL = NULL ; 100000 * NULL = NULL
- 9. •Not Null NOT NULL will ensure at least some value should be present in a column • Unique It will not allow any duplicates in a column UNIQUE column can take multiple NULL (s)
- 10. • Primary Key It is the combination of NOT NULL and UNIQUE Only one PK is allowed in a table PK identifies a record uniquely in a table Creation of PK is not mandatory, but it is highly recommended to create Candidate Key: Eligible to become PK Alternate Key: Eligible to become primary key but not chosen as PK CK=PK+AK AK=CK-PK
- 11. • Foreign Key FK creates relationship between any two tables FK is also called as referential integrity constraints FK is created on the child table FK can take both NULL and duplicate values To create FK, the master table should have PK defined on the common column of the master table We can have more than 1 FK in a given table
- 12. •Check It is used to provide additional validations as per the customer requirements.