Update Query

The original comment:

I have Tables A and B

Table_A:
+--------+-----------+
| Cust_ID| Name
| 1 | Mark |
| 2 | Jane |
| 3 | James |
|+-------+-----------+

Table_B:
+--------+---------------------+
| Cust_ID| Email |
| 1 | mark@yahoo.com |
| 2 | jane@hotmail.com |
| 3 | |
| | alex@hotmail.com |
+--------+--------------------+


I need to update Table_A with fields in Table_B with this result:

+--------+-----------+------------------+
| Cust_ID| Name | Email |
| 1 | Mark | mark@yahoo.com |
| 2 | Jane | jane@hotmail.com |
| 3 | James | |
| 4 | | alex@hotmail.com |
|+-------+-----------+------------------+

UPDATE TABLE_A LEFT JOIN TABLE_B ON TABLE_A.CUST_ID= TABLE_B.CUST_ID

I do not think this one will work. There seems to be some error with
it.

Also, my table A and B are very big in size. I am afraid system will
hang since there are over thousands of data. To prevent this, I will like to
add a column to Table B call 'Flag'. When the data is successfully
transfered, flag= 1. Else, flag= null. Hence this way, even if system
hangs, I am aware of what data is being transferred, what is not.

I do not think I can add an If-else statement in the SQL query. If so,
how
do I ensure that data is being transferred over before changing flag=
1?

UPDATE TABLE_A LEFT JOIN TABLE_B ON TABLE_A.CUST_ID= TABLE_B.CUST_ID

How will this command work without a SET clause in it???

Create an email field in Table A which will b blank before updation.
Then use,


UPDATE TABLE_A SET TABLE_A .emailid = TABLE_b .emailid where TABLE_A.CUST_ID= TABLE_B.CUST_ID


Pls check the exact syntax . This should work .

gururaj0@yahoo.com