SQL Interview Questions on "SQL Table Scripts"
71. Write create table syntax for employee tableOracle -CREATE TABLE EMPLOYEE (
EMPLOYEE_ID NUMBER,
FIRST_NAME VARCHAR2(20 BYTE),
LAST_NAME VARCHAR2(20 BYTE),
SALARY FLOAT(126),
JOINING_DATE TIMESTAMP (6) DEFAULT sysdate,
DEPARTMENT VARCHAR2(30 BYTE) )
SQL Server -CREATE TABLE EMPLOYEE(
EMPLOYEE_ID int NOT NULL,
FIRST_NAME varchar(50) NULL,
LAST_NAME varchar(50) NULL,
SALARY decimal(18, 0) NULL,
JOINING_DATE datetime2(7) default getdate(),
DEPARTMENT varchar(50) NULL)
72. Write syntax to delete table employee
DROP table employee;
73. Write syntax to set EMPLOYEE_ID as primary key in employee table
ALTER TABLE EMPLOYEE add CONSTRAINT EMPLOYEE_PK PRIMARY KEY(EMPLOYEE_ID)
74. Write syntax to set 2 fields(EMPLOYEE_ID,FIRST_NAME) as primary key in employee table
ALTER TABLE EMPLOYEE add CONSTRAINT EMPLOYEE_PK PRIMARY KEY(EMPLOYEE_ID,FIRST_NAME)
75. Write syntax to drop primary key on employee table
Alter TABLE EMPLOYEE drop CONSTRAINT EMPLOYEE_PK;
76. Write Sql Syntax to create EMPLOYEE_REF_ID in INCENTIVES table as foreign key with respect to EMPLOYEE_ID in employee table
ALTER TABLE INCENTIVES ADD CONSTRAINT INCENTIVES_FK FOREIGN KEY (EMPLOYEE_REF_ID) REFERENCES EMPLOYEE(EMPLOYEE_ID)
77. Write SQL to drop foreign key on employee table
ALTER TABLE INCENTIVES drop CONSTRAINT INCENTIVES_FK;
78. Write SQL to create Orcale Sequence
CREATE SEQUENCE EMPLOYEE_ID_SEQ START WITH 0 NOMAXVALUE MINVALUE 0 NOCYCLE NOCACHE NOORDER;
79. Write Sql syntax to create Oracle Trigger before insert of each row in employee table
CREATE OR REPLACE TRIGGER EMPLOYEE_ROW_ID_TRIGGER
BEFORE INSERT ON EMPLOYEE FOR EACH ROW
DECLARE
seq_no number(12);
BEGIN
select EMPLOYEE_ID_SEQ.nextval into seq_no from dual ;
:new EMPLOYEE_ID :=seq_no;
END;
SHOW ERRORS;
80. Oracle Procedure81. Oracle View
An example oracle view script is given below
create view Employee_Incentive as select FIRST_NAME,max(INCENTIVE_AMOUNT) INCENTIVE_AMOUNT from EMPLOYEE a, INCENTIVES b where a.EMPLOYEE_ID=b.EMPLOYEE_REF_ID group by FIRST_NAME
82. Oracle materialized view - Daily Auto Refresh
CREATE MATERIALIZED VIEW Employee_Incentive
REFRESH COMPLETE
START WITH SYSDATE
NEXT SYSDATE + 1 AS
select FIRST_NAME,INCENTIVE_DATE,INCENTIVE_AMOUNT from EMPLOYEE a, INCENTIVES b
where a.EMPLOYEE_ID=b.EMPLOYEE_REF_ID
83. Oracle materialized view - Fast Refresh on Commit
Create materialized view log for fast refresh. Following materialized view script wont get executed if materialized view log doesn't exists
CREATE MATERIALIZED VIEW MAT_Employee_Incentive_Refresh
BUILD IMMEDIATE
REFRESH FAST ON COMMIT AS
select FIRST_NAME,max(INCENTIVE_AMOUNT) from EMPLOYEE a, INCENTIVES b
where a.EMPLOYEE_ID=b.EMPLOYEE_REF_ID group by FIRST_NAME
84. What is SQL Injection ?
SQL Injection is one of the the techniques uses by hackers to hack a website by injecting SQL commands in data fields.
