what is difference between "Primary key" and "Unique key"?

4 Answers   PreVator,

---

Create table emp (id number(9), name varchar2(20),salary number(9,2)); The table has 100 records after table created.Now i nee to change id's Datatype is to be Varchar2(15). now Alter table emp modify(id varchar2(15),name varchar2(20), salary number(9,2)); Whether it will work or returns error? post answer with explanation.

13 Answers   Oracle, TCS,

---

What is a natural join sql?

0 Answers  

---

What is interval partition?

0 Answers  

---

How many sql are there?

0 Answers  

---

Write the order of precedence for validation of a column in a table? I. Done using database triggers. Ii. Done using integarity constraints

0 Answers  

---

Explain cursor types?

0 Answers  

---

How to fix oracle error ora-00942: table or view does not exist

0 Answers  

---

How would you go about increasing the buffer cache hit ratio? 0. Explain the difference between a hot backup and a cold backup and the benefits associated with each 1. You have just had to restore from backup and do not have any control files. How would you go about bringing up this database? 2. How do you switch from an init.ora file to a spfile? 3. Explain the difference between a data block, an extent and a segment. 4. Give two examples of how you might determine the structure of the table DEPT. 5. Where would you look for errors from the database engine? 6. Compare and contrast TRUNCATE and DELETE for a table. 7. Give the reasoning behind using an index. 8. Give the two types of tables involved in producing a star schema and the type of data they hold. 9. What type of index should you use on a fact table? 10. Give two examples of referential integrity constraints. 11. A table is classified as a parent table and you want to drop and re-create it. How would you do this without affecting the children tables? 12. Explain the difference between ARCHIVELOG mode and NOARCHIVELOG mode and the benefits and disadvantages to each. 13. What command would you use to create a backup control file? 14. Give the stages of instance startup to a usable state where normal users may access it. 15. What column differentiates the V$ views to the GV$ views and how? 16. How would you go about generating an EXPLAIN plan?

2 Answers  

---

What is triggering circuit?

0 Answers  

---

What is normalization? How many normalization forms are there?

0 Answers  

---

Why is there a need for sqlcode and sqlerrm variables?

0 Answers  

---