[英]How to UPDATE column with ROW_NUMBER() in Teradata?
I'm having a table like this 我有这样的桌子
Create table test1(emp_id decimal(5,0), emp_name varchar(20));
Insert into test1(2015,'XYZ');
Insert into test1(2016,'XYZ2');
Now I want to update emp_id to row_number() or add new column into same table like (emp_no integer) to row_number(). 现在,我想将emp_id更新为row_number()或将新列添加到同一表中,例如将(emp_no integer)添加到row_number()。
can anyone please tell me the query for this? 谁能告诉我这个查询吗?
You need to use UPDATE FROM: 您需要使用UPDATE FROM:
UPDATE test1
FROM
( SELECT ROW_NUMBER() OVER (ORDER BY emp_id) AS rn,
emp_id
FROM test1
) AS src
SET emp_id = src.rn
WHERE test1.emp_id = src.emp_id -- must be unique column(s)
Btw, instead of updating all rows of a table it might be better to INSERT/SELECT or MERGE the SELECT into a new table. 顺便说一句,与其更新表的所有行,不如将INSERT / SELECT或SELECT合并到新表中可能更好。 You must do it if there's no unique column, you should if
emp_id
is the PI of your table (otherwise performance will be horrible). 如果没有唯一列,你必须做到这一点,你应该如果
emp_id
是你的表的PI(否则性能会可怕)。
Create table test1(
emp_id decimal(5,0),
emp_name varchar(20),
emp_no INTEGER GENERATED ALWAYS AS IDENTITY
(START WITH 1
INCREMENT BY 1
)
);
Insert into test1(2015,'XYZ1',2);
Insert into test1(2016,'XYZ2',2);
Insert into test1(2015,'XYZ3',null);
Insert into test1(2016,'XYZ4',null);
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