Lecture11.txt

Lecture-10:
Update Statement in SQL:

Update: It is used to modify existing records.
Why we need to update data:
1.	User Experience
2.	Cost
3.	Storage
Example: Amazon => Database => Customer
                SlNo              Name                     Address                         Age
                 1.               Rupu                     Agarpara                         22
                 2.               Rup                 Salt Lake, Sector-2                   20
                 3.               Rupayan                   Fulia                           24
                 4.               Rupi                      Newtown                         21
[Note: Sl. No. 2 Customer named “Rup” entered the wrong address by mistake. Now, he have to update his “Address” in Amazon’s database]
Syntax: update table_name 
               set want_toUpdate_column_name 
               where unique_column_name= ”condition”;
Command: update Customer set Address=”Salt Lake, Sector-5” where SlNo= 2;
Output:
                SlNo              Name                     Address                         Age
                 1.               Rupu                     Agarpara                         22
                 2.               Rup                 Salt Lake, Sector-5                   20
                 3.               Rupayan                   Fulia                           24
                 4.               Rupi                      Newtown                         21
Important Points:
1.	Always use where clause with update statement.
2.	Risky Command.
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