php mysql只更新空列

Question

Consider I have 4 columns in a table and i have datas for 3 columns like below

TableTest

Col1  | Col2  | Col3
D11   | D12   |   
D21   | D22   | 

Normally the update query would be

Update TableTest SET Col1 = D11 , Col2 = D12 , COL3 = newdata Where Col1= D11

The Scenario is , the update query should only push data to the COL3 , it should skip the Col1 and Col2, as it has already filled with data(even if same or different data for the Col1 and Col2)

Answer 1

This might help -

UPDATE TableTest a
INNER JOIN TableTest b ON a.Col1 = b.Col1
SET a.Col3 = 'newData'
WHERE a.Col3 IS NULL

An INNER JOIN with the same table so that it updates the appropriate row!

Answer 2

If you just want to update COL3 than don't include other columns in UPDATE query.

Query:

Update TableTest SET COL3 = newdata Where Col1= D11

Answer 3

You should update whole table using single query as:

Update TableSet SET COL3=CONCAT('D',CONVERT(Substr(Col2,2),INT)+1)

This will update table as follows:

TableTest

Col1  | Col2  | Col3
D11   | D12   |  D13 
D21   | D22   |  D23

Answer 4

就这样做，像这样：

Update TableTest SET  COL3 = newdata Where Col1= D11

Answer 5

In UPDATE query, there is no need to reassign the value of col1 and col2 if those values are not changing.

UPDATE TableTest 
SET COL3 = newdata 
WHERE Col1= 'D11';