Luis Cazares - Monday, March 27, 2017 9:57 AM

Here are my suggestions depending on the data type.
DECLARE @NUMLIST TABLE
(
NM_ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY CLUSTERED
,SKU BIGINT  NOT NULL
);
INSERT INTO @NUMLIST(SKU)
VALUES (7856614),(7956615),(7956616),(7756616),(795661);

DECLARE @NUMDIG INT = 6;

SELECT long.NM_ID,
  long.SKU,
  ISNULL(short.SKU, long.SKU) AS matching
FROM @NUMLIST long
LEFT
JOIN @NUMLIST short ON (long.SKU / 10 = short.SKU AND LEN( long.sku) = @NUMDIG + 1)
GO

DECLARE @NUMLIST TABLE
(
NM_ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY CLUSTERED
,SKU varchar(15)  NOT NULL
);
INSERT INTO @NUMLIST(SKU)
VALUES (7856614),(7956615),(7956616),(7756616),(795661);

DECLARE @NUMDIG INT = 6;

SELECT long.NM_ID,
  long.SKU,
  ISNULL(short.SKU, long.SKU) AS matching
FROM @NUMLIST long
LEFT
JOIN @NUMLIST short ON (long.SKU LIKE short.SKU + '_' AND LEN( long.sku) = @NUMDIG + 1)