Sql: Originally called "Structured Query Language"; but sometime its also called "Standared Query Language".
SQL is the Standared Language for dealing with Relational Databases, & it is Supported by just about every Product on the Market.
SQL was Originally developed in IBM Research in the early 1970. The Current version of the Standard known informally as SQL/92, The official name is International Standard Database Language SQL(1992).
sql was originally intended to be a "data Sublanguage" specifically. Finally, it has to be said that sql is very far from being the perfect relational language, it suffers sins of both Omission & Commission.
sql includes both data definition operations & data mainipulation operations. The data mainipulation language (DML) can operate at both the external level & the conceptual level on database table. The sql data definition language (DDL) can be used to define objects at the external level, the conceptual level, & even in most commercial System.
Sql also provides certain data control facilities:- i.e., facilities that cann't really be classified as either DDL or the DML.
Data Definition Operation are that in which we define the data. Example: we use, in Create table Statement Specifies the name of base table to be created, the names & Data types of the columns of that table & Primery & any foreign keys in that table.
Sql Manipulation Operation are Select, insert, update & delete.
The SQL Statements can be Embedded ,meaning they can be intermixed with the programming languages Statements. In the Embedded case, moreover the application Program can typically be written in a varity of host languages: cobol, java, PL/I, etc.
Dynamic Sql consists of a set of embedded Sql facilities that are intended to support the construction of generalized, online, & Possibly interactive operations.
BASIC OF TABLES
In a DBMS (database management system) a group of similar information or data which is of interest to an organization, is called an entity. entity information is stored in an object called Table. for example: a client is considerd an entity, Information about the client entity can be stored in a client-master table.
A Table is really a two Dimentional matrix that consists of rows & columns. The table must have a unique name.
Elements of a Table:
Attributes:- each entity can have number of charecteristics, A client can have charecteristics like name, Address, telephone, fax, balance, etc. The charecteristics of an entity are called Attributes, It also called columns or fields.
Tuple/Record/Row:- An organization will deal with meny clients and the same information must be recorded for each client, Multiple fields placed in a horizonal place, is called a Records or Row.
for create table we used the create statement.
syntax:- CREATE TABLE tablename (columnname, columnname datatype(size),columnname datatype(size));
INSERTION OF DATA INTO TABLE:-
sYntax:- INSERT INTO tablename (columnname,columnname) VALUES (expression,expretion);
example:- Insert into client (client_id,name,city) values (oo51,'alok','modinagar');
Once data has been inserted into a table the next most logical operation would be to view what has been entered .the selected statement is used to achieve this.
Select is not verb
When data from all rows and column from the table are to be viewed the syntax of the select statement will be .
Select from table name
Oracle allows the user to user to use the meta character asterisk which is expanded by oracle to mean all column in the table
When we want to view some specific column in the table
Select From table name
Example: - retrieve the names of the employees and their salaries from the table emp.
Select name salary from emp;
Filtering table data. While viewing data. it is rare that all data from the table will be required each time . So sql must give us a method of filtering out data that is not required.
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