SQL 服务器覆盖违反唯一约束

Question

I have two files which I am importing via Node JS to SQL Server. The table has unique key for equity instrument identifier (ISIN)

data1.csv and data2.csv

I first import data1.csv each row is inserted to the database. After this I import data2.csv (the values are again inserted to database) which may contain the same ISIN, but it's related values are higher priority than the first file (there are not many of these ISINs 5 out of 1000 or so).

What can I do with SQL server to overwrite the values if the unique constraint is violated? I understand that there is an option to upload data2.csv first, however there are some external constrains that do not allow me to do that.

Please tell me if additional information is required

Answer 1

I would recommend staging process to do this:
1. create a staging table with similar schema as your target table
2. Before loading delete all rows from staging table (you can use truncate)
3. Upload the file to the staging table
4. Load your data into final table - here you can use some logic to only insert new rows and update existing rows. Merge command will be useful in scenario like this.

Repeat steps 2 to 4 for each source table.