Answer / ashis kumar jena

A primary key is one which uniquely identifies a row
of a table.
This key does not allow null values and also
does not allow duplicate values.
Each table should have a primary key, and each table can
have only one primary key.

Answer / perumal

1. Primary Key Doesn't allow the NULL values and also
does not allow duplicate values.

2. Primary Key has the Unique Columns.

3. Primary Key Uniquely Identify the each row of the tables.

Answer / hannan oca

primary key =notnull+unique value in column

a table consist of only one primary key.

Example

a primary key is like a father in house, like only one but
there may be a lot of childs just like columns.

Answer / satheeh

Primary key is nothing but restriction or condition or constraint given to a specific column to avoid the null and duplicate values.
primary key=not null+unique
that means primary key performs both operations at a time.
primary key plays vital role when relationship between two or more tables

How to write a procedure for displying the data in a TREE or (PARENT and CHILD ) relationship , for ex: A is the main project id, for this project B,C,D are sub tasks(sub project id's) for B the sub tasks are e,f,g and for c is h ,i ,j and for d is k,l,m now i need to display the o/p in a TREE fashion pls help me , thanks in advance surendra

2 Answers   Zensar,

---

What is a schema? How is it useful in sql servers?

0 Answers  

---

which will default fire first  statement level trigger or row level trigger

2 Answers   Cap Gemini, Data Vision,

---

How do you exit in sql?

0 Answers  

---

Can a composite key be null?

0 Answers  

---

What does trigger mean in psychology?

0 Answers  

---

Explain the difference between triggers and constraints?

0 Answers  

---

how to calculate expressions with sql statements? : Sql dba

0 Answers  

---

What are primary key and foreign key and how they work?

0 Answers  

---

How to execute OS(operating system) command from pl/sql?

3 Answers  

---

What is a mutating table and a constraining table?

0 Answers  

---

How to run sql commands in sql*plus?

0 Answers  

---