Oracle SQL FAQ

Alter trigger trigger_name disable/enable all triggers.

Alter trigger Disable;

Yes We can. If we use the combination "unique+not null" the referential integrity is not maintained and that is not the case with primary key.

There is only one primary key per table but we can use unique and not null constraints more than one column in a table. Primary key having both functionality as it can not be null but unique.

No, you cant insert column between existing columns in oracle database but, you can add or insert column in a table at end of last column.

Oracle doesnt allow inserting column in between two. But there are work around to do this. Simple and best one is to add the new column at the end of table. Then rename that table, renaming table will...

Its impossible to avoid duplication without constraint the PK on Column

We must constraint the column with primary key when designing the database to avoid the duplications.

By using merge statement we can do it simply.

Use merge stat

Code
SELECT * FROM EMP 
WHERE (ROWID,1) IN (SELECT ROWID,MOD(ROWNUM,2) FROM EMP);
 
OR 
 
SELECT * FROM (SELECT EMP.*,ROWNUM K FROM EMP)
WHERE MOD(k,2)=0;

Code
SELECT * FROM table_name WHERE mod(primary_key_column,2)=0 --to find even rows in a table
 
SELECT * FROM employees WHERE mod(employee_id,2)=0 --to find even rows in a table
 
SELECT * FROM employees WHERE mod(employee_id,2)=1 --to find odd rows in a table

Select clause is must for retrieving data from the database. You cant retrieve data without select clause.

Impossible! Rows will not be rerieved without select keyword.

SEE THIS ALSO,

Code
SELECT EMPNO,ENAME,JOB,COMM
FROM EMP
ORDER BY COMM NULLS LAST;

Nulls are unassigned and unavailable values.i.e. null means "no value".

So in order to obtain values the values get preference over the no values(null).

g means Grid Computing..

grid computing

"sql SELECT DISTINCT d1.depno, e1.salary,e1.empid,d1.location FROM EMPLOYEE1 e1, dept d1 WHERE 2 = (SELECT count(DISTINCT e2.salary) FROM EMPLOYEE1 e2...

Code
SELECT min(salary) 
FROM dept
WHERE salary IN ( SELECT DISTINCT top 2 salary
                        FROM dept
                        ORDER BY salary DESC)

no data found is an exception where as %not found is a cursor attribute.

no data found is exception where as %notfound is retrn by exception

Use DML Triggers to apply the same action to another table as well.

write trigger

Explain plan will tell you

use select may be this works

There is no option to avoid duplicates when inserting data from flatfiles using sql*loader.

The best way is load the data into staging table and write the
query to eliminate the duplicate rows.

use PK or unique key

Left outer Join fetch all the records from Left side Table(Only Condition satisfied records from right side table) where as Right Outer Join fetch all the records from Right side Table(Only Condition satisfied records from Left side table).

Using Equi Join with Union we can do the outer join then why we need to go for Outer Join -- increase the performance

Answer:

Code
INSERT ALL
    INTO first_table VALUES(value1,value2)
     INTO second_table VALUES(value1,value2)
 
SELECT * FROM dual;

Using merge concept, we can insert a record at a time into two tables.

The below code selects the exact middle row from the table

Code
SELECT * FROM TABLE WHERE rownum=trunc(SELECT count(*)/2 FROM TABLE) 

The below code returns the rows from 50-74

Code
TO SELECT the middle rows:
        SELECT * FROM TABLE offset 50 rows fetch next 25 rows only
             

1.Sql is a declarative language.It tells only what to do. PL/Sql is a procedural language.It tells what to do and how to do. 2.Sql executes DDL and DML statements . Pl/Sql executes triggers,func...

sql is structured query language and plsql is procedural sql. in sql we write a query to fetch the data from data base. in pl sql we write the set of sql command and execute it in one times. the benef...

Delete: Deletes the contents of the table.Also allows us to delete particular row(s) by condition.We can undo the delete operation and write trigger on delete action. Truncate: Delete the ...

delete:delets the records from the table by using where claus
truncate:removes all the records from the table and frees the space containing by the table
drop:drops the table and its structure