Answer Posted / saraswathi muthuraman

Compost key :

More than one column will be used to create compst key

SQL> create table ts_250 (a number,b number,c number,
primary key(a,c));

Table created.

here column A and column C is used to create compst key.
U can't insert null value in both columns.
Only unique combination of column A and column B value can
be inserted.

Primary key :

Key will be created on a single column in table.

SQL> create table ts_251 (a number,b number,c number,
primary key(a));

Table created.


null value cann't be inserted into column a.
oracle will create a index
only unique value can be inserted into column a.
only one primary key can be created on a table

What is mysql default database?

906

---

Can you rename a database in mysql?

949

---

How to Recover a MySQL root password. Stop the MySQL server process. Start again with no grant tables. Login to MySQL as root. Set new password. Exit MySQL and restart MySQL server.

945

---

What is the use of mysqli_fetch_array?

967

---

Write command to import an mysql file?

963

---

How do you select a table?

883

---

What is user in mysql?

808

---

What is the password of mysql?

908

---

What command is used to delete the data from the table without deleting the table structure?

898

---

Write a query to retrieve a hundred books starting from 20th.

1458

---

How do I find the size of a mysql database?

857

---

Is mysql query case sensitive?

901

---

how to add a new column to an existing table?

936

---

What are the difference between mongodb and mysql?

1253

---

What are the column comparisons operators?

1171

---