Question

I have a table that contains two columns

ID | Name
----------------
1  | John
2  | Sam
3  | Peter
6  | Mike

It has missed IDs. In this case these are 4 and 5.

How do I find and insert them together with random names into this table?

Update: cursors and temp tables are not allowed. The random name should be ‘Name_’+ some random number. Maybe it would be the specified value like ‘Abby’. So it doesn’t matter.

Answer 1

Using a recursive CTE you can determine the missing IDs as follows

DECLARE @Table TABLE(
        ID INT,
        Name VARCHAR(10)
)

INSERT INTO @Table VALUES (1, 'John'),(2, 'Sam'),(3,'Peter'),(6, 'Mike')

DECLARE @StartID INT,
        @EndID INT

SELECT  @StartID = MIN(ID),
        @EndID = MAX(ID)
FROM    @Table

;WITH IDS AS (
        SELECT  @StartID IDEntry
        UNION ALL
        SELECT  IDEntry + 1
        FROM    IDS
        WHERE   IDEntry + 1 <= @EndID
)
SELECT  IDS.IDEntry [ID]
FROM    IDS LEFT JOIN
        @Table t    ON  IDS.IDEntry = t.ID
WHERE   t.ID IS NULL
OPTION (MAXRECURSION 0)

The option MAXRECURSION 0 will allow the code to avoid the recursion limit of SQL SERVER

From Query Hints and WITH common_table_expression (Transact-SQL)

MAXRECURSION number Specifies the maximum number of recursions
allowed for this query. number is a nonnegative integer between 0 and
32767. When 0 is specified, no limit is applied. If this option is not specified, the default limit for the server is 100.

When the specified or default number for MAXRECURSION limit is reached
during query execution, the query is ended and an error is returned.

Because of this error, all effects of the statement are rolled back.
If the statement is a SELECT statement, partial results or no results
may be returned. Any partial results returned may not include all rows
on recursion levels beyond the specified maximum recursion level.

Generating the RANDOM names will largly be affected by the requirements of such a name, and the column type of such a name. What exactly does this random name entail?