SQL Query to fill column with combination of other columns

问题

I have table with this structure

ID | Parameter1 | Parameter 2  | Multiplication
1  |     1024   |     100      |
2  |     1200   |     200      |
3  |     1600   |     300      |
4  |     1900   |     400      |

I want to fill column Multiplication with combined string from Parameter 1 and Parameter 2

ID | Parameter1 | Parameter 2  | Multiplication
1  |     1024   |     100      |   1024_100
2  |     1200   |     200      |   1200_200
3  |     1600   |     300      |   1600_300
4  |     1900   |     400      |   1900_400

Help me please to create this SQLQuery

回答1:

Using SQL then the following query should work..

Assuming the Param fields are ints use cast to make them strings

UPDATE Table1 SET Multiplication = CAST(Parameter1 AS VARCHAR(10)) + '_' + CAST(Parameter2 AS VARCHAR(10))

Else if they are already strings (e.g., varchar, text) just don't cast. I.e.,

UPDATE Table1 SET Multiplication = Parameter1 + '_' + Parameter2

Just change Table1 to the name of your table

回答2:

An alternate for SQL Server is to add a column to handle this for you. It will automatically update the value if either parameter1 or parameter2 changes:

ALTER TABLE myTable
    ADD myJoinedColumn AS CAST(Parameter1 AS VARCHAR(10)) + '_' + CAST(Parameter2 AS VARCHAR(10))

Or as @Scozzard mentions in his answer, if they are already strings:

ALTER TABLE myTable
    ADD myJoinedColumn AS (Parameter1 + '_' + Parameter2)

回答3:

For MySQL:

update Table1 set
    Multiplication = concat(cast(Parameter1 as char), '_', cast(Parameter2 as char))

More about cast and concat in MySQL 5.0 Reference Manual.

回答4:

update Table1 set Multiplication = CONCAT_WS('_',Parameter1,Parameter2)

回答5:

update tablename
set Multiplication = convert(varchar, Parameter1) + '_' + convert(varchar, Parameter2)

来源：https://stackoverflow.com/questions/9126202/sql-query-to-fill-column-with-combination-of-other-columns

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mysql

sql

sql-update