Oracle SQL & PL/SQL

This clause in a select statement arranges the data on a specified column in ascending or in descending order. This clause will work after the execution of select statement. By default it arranges the data in ascending order. In order to arrange the data in descending order , an option called DESC is used. Data is arranged in order over a required column for temporary. Order by clause can be specified with one or more columns.       Examples :-         Display empno, ename and salary of all the employees arranging salaries in ascending order.           Ans : Select empno, ename, sal from emp order by sal;           Display ename, job, salary, deptno, commission, and hiredate of all those employees  who are working as CLERK, SALESMAN and they have been hired in the year 81 and they don’t earn any commission. Arrange the data in ascending order of salary.    ...

This operator tests for NULL values. It is the only operator that can be used to test for NULL’s. The negation is IS NOT NULL.       Examples :-        Select ename, deptno, comm from emp where comm IS NULL;         Select ename, deptno, comm from emp where comm IS NOT NULL;         Select ename, deptno, job, mgr from emp where mgr IS NULL;         Select ename, deptno, job, mgr from emp where mgr IS NOT NULL; HOME

This operator is used to test for values in a specified list. This operator can be used upon any data type. The negation of the operator is NOT IN.       Examples :-       Select ename, sal, job from emp where ename IN(‘ALLEN’ , ‘SCOTT’);         Select ename, sal, job from emp where ename NOT IN(‘ALLEN’ , ‘SCOTT’);         Select ename, sal, job, deptno from emp where deptno IN(10,30);         Select ename, sal, job, deptno from emp where deptno NOT IN(10,30);         Select ename, sal, hiredate from emp where hiredate IN(’02-APR-81’ , ’12-JAN-83’);         Select ename, sal, hiredate from emp where hiredate NOT IN(’02-APR-81’ , ’12-JAN-83’); HOME

This operator is used to display rows based on a range of values. The declared range is inclusive. The lower limit should be declared first. The range that you specify contains a lower limit and an upper limit. Examples :-           Select ename, sal, job from emp w here sal BETWEEN 1000 AND 2000;           Select ename, sal, job from emp where sal NOT BETWEEN 1000 AND 2000;           Select ename, sal, job from emp where job BETWEEN ‘MANAGER’ AND ‘SALESMAN’;          Select ename, sal, job from emp where job NOT BETWEEN ‘MANAGER’ AND ‘SALESMAN’;          Select ename, sal, job, hiredate from emp where hiredate BETWEEN ’02-APR-81’ AND ’12-JAN-83’;          Select ename, sal, job, hiredate from emp where hiredate NOT BETWEEN ’02-APR-81’ AND ’12-JAN-83’; HOME

Supressing Duplicate Rows : = Sometimes, your query results contain duplicate rows. You can eliminate such rows by adding  the keyword DISTINCT immediately after the keyword SELECT. Multiple columns can be declared after the DISTINCT qualifier. The DISTINCT qualifier affects all the selected columns, and represents a DISTINCT combination of the columns. When DISTINCT is implemented upon a column which may contain NULL values, all the NULLS in the column together treated as one DISTINCT group. A select statement should have one DISTINCT keyword. Examples :=           Ø   Select DISTINCT deptno from emp;             Ø   Select DISTINCT deptno,mgr from emp;   Ø   Select DISTINCT deptno,job from emp;        HOME

Wild Charcters :- These characters are used to provide pattern matching which means comparision to data is provided with partial value. ORACLE provides the following wild characters.            i)      _(Underscore) -> Represents single character.             ii)      %(Percentage) -> Represents group of character. Ø   Inorder to have wild characters for the comparision to partial data, LIKE operator is used. Ø   If these wild characters are formed in data, then the wild characters can be converted to data using ‘\’ (backslash). It is represented through an option called ‘ESCAPE’ , which is written after like operator. Examples :- Display employee number and employee name of all those employees whose names contain 4 characters. Ans : select empno, ename from emp           Where ename LIKE ‘---...

This clause is used to provide comparison of data, which restricts the rows from a table. A WHERE clause contains a condition that must be met and should directly follow the from clause. Comparison to date type data is not case sensitive. Character values are case sensate and Date values are format Sensitive (DD-MON-YY). The WHERE clause can compares..       Ø   Values in columns         Ø   Literal Values         Ø   Arithmetic Expressions         Ø   Function Examples :- Display all those employees, who are working as CLERK. Ans : Select * from emp where job = ‘CLERK’; Display all those employees, who are working in deptno 20. Ans : Select * from emp where deptno=20; Display all those employees, who have been hired on 3 rd -dec-81. Ans : Select * from emp where hiredate=’3 rd -dec-81’; Display empno,ename,job,sal,deptno for all those empl...