Most Elegant Way to Populate Nulls from Reference Table

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I have two tables like so:

Table 1:

Column 1  Column 2
A            1
B            NULL
C            3
D            4

Table 2:

Column 1  Column 2
A            1
B            2
C            3
D            4

I receive the data in table 2 on a time delay, and what I need to do when I receive it is populate the null values in Table 1 with the data in table 2. Is there an elegant way to do this in Standard SQL without making temporary tables or using sub-queries?

Thanks!


Consider using a MERGE statement:

MERGE dataset.table1 AS t1
USING dataset.table2 AS t2
ON t1.column1 = t2.column1
WHEN MATCHED THEN
  UPDATE SET t2.column2 = t1.column2

Take a look at the supported actions you can perform; if you want to insert new rows, you can do that using MERGE as well.

T-SQL Querying, the CROSS APPLY operator, and then refer to it in the query's WHERE clause, like This query generates the following output where the rows with a NULL in the more elegant way to achieve unpivoting compared to the previous method. a task, I'll use a table called Sales that you create and populate by running the​  CLR nullable value types are not intended for storage of database nulls because an ANSI SQL null does not behave the same way as a null reference (or Nothing in Visual Basic). For working with database ANSI SQL null values, use System.Data.SqlTypes nulls rather than Nullable .


You can use the UPDATE statement from the DML (Data Manipulation Language) and update Table 1 in place.

It is not clear from your question how you receive data from Table 2, so I will assume that you have a temporary table called Table2. You will have to JOIN Table1 and Table2 in order to find which rows have NULL values, i.e Table1.Column2 IS NULL. Then update Column2 in those rows using the value in Table2. It should be something like this:

UPDATE Table1
SET Column2 = Table2.Column2
FROM
  Table1 LEFT JOIN Table2 USING(Column1)
WHERE
  Table1.Column2 IS NULL

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Correct use of UPDATE statement would be

UPDATE `project.dataset.table1` a
SET Column_2 = b.Column_2
FROM `project.dataset.table2` b
WHERE a.Column_1 = b.Column_1
AND a.Column_2 IS NULL

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InfoWorld, Where you intend to reference a label in another module, you can identify it as external to the program. to fill a block with a specified number of characters, such as nulls or spaces. You can nest as many as four files, one included file including yet another. The cross-reference table can print a list of all the line numbers  You can leave the FK to some dimension tables as NULL if those dimensions are not known or not applicable. You just have to remember to use outer joins when you do your reporting query. Alternatively, some people create a "none" and/or an "n/a" dimension record for data mart dimensions and then populate fact table FKs to point at these rather


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