I was curious so I set up a test table with 100,000 rows of random names with some double-names (i.e., with an ampersand) randomly thrown in.
I tested selecting the rows with ampersands via LIKE and CHARINDEX in the where clause and then doing the actual update. Then, out of curiosity, I also tried using DelimitedSplit8K to split the target column with a CROSS APPLY to get the rows to update.
I just did a very simple test using client statistics and I know that isn't the most accurate way to measure performance. Based on that, the differences between LIKE and CHARINDEX are negligible with the split string and join method following close behind. However, I'd bet that if the operation required finding more than a single character the split and join would come out ahead.
FWIW, here's the code I used for testing.
--Code to generate some random names came from this post
--http://www.sqlservercentral.com/Forums/FindPost428949.aspx
IF OBJECT_ID('tempdb..#randomFullname') IS NOT NULL
DROP TABLE #randomFullname
IF OBJECT_ID('tempdb..#firstname') IS NOT NULL
DROP TABLE #firstname
IF OBJECT_ID('tempdb..#lastName') IS NOT NULL
DROP TABLE #lastName
IF OBJECT_ID('tempdb..#NamesToUpdate') IS NOT NULL
DROP TABLE #NamesToUpdate
CREATE TABLE #randomFullname (
rid INT IDENTITY(1,1) NOT NULL,
fnid INT NOT NULL,
lnid INT NOT NULL,
PRIMARY KEY (rid))
CREATE TABLE #firstname (
fnID INT IDENTITY(1,1) NOT NULL,
FName varchar(100) NULL,
PRIMARY KEY (fnID))
CREATE TABLE #lastName (
lnID INT IDENTITY(1,1) NOT NULL,
LName varchar(100) NULL,
PRIMARY KEY (lnID))
CREATE TABLE #NamesToUpdate (
rid INT NOT NULL,
LName varchar(100) NOT NULL,
FName varchar(100) NOT NULL,
PRIMARY KEY (rid))
INSERT #firstname (FName)
SELECT 'Matt' UNION ALL
SELECT 'Jeff' UNION ALL
SELECT 'Jason' UNION ALL
SELECT 'Mark' UNION ALL
SELECT 'Andrew' UNION ALL
SELECT 'Bob' UNION ALL
SELECT 'Joe' UNION ALL
SELECT 'Steve' UNION ALL
SELECT 'Kelly' UNION ALL
SELECT 'Beverly' UNION ALL
SELECT 'Janet' UNION ALL
SELECT 'Angela' UNION ALL
SELECT 'Brandie' UNION ALL
SELECT 'Josephine'
INSERT #lastName (LName)
SELECT 'Miller' UNION ALL
SELECT 'Moden' UNION ALL
SELECT 'Smith' UNION ALL
SELECT 'Jones' UNION ALL
SELECT 'Tarvin' UNION ALL
SELECT 'ODoul' UNION ALL
SELECT 'Dupont' UNION ALL
SELECT 'Kelley' UNION ALL
SELECT 'Taylor' UNION ALL
SELECT 'Barton'
DECLARE
@fncount int,
@lncount int
SELECT @fncount = count(*) FROM #firstname
SELECT @lncount = count(*) FROM #lastName
INSERT INTO #randomFullname (fnid,lnid)
SELECT TOP 100000
cast(rand(checksum(newid()))*(@fncount-1) as int)+1,
cast(rand(checksum(newid()))*(@lncount-1) as int)+1
FROM Master.dbo.SysColumns t1,
Master.dbo.SysColumns t2
INSERT INTO #NamesToUpdate (rid,LName,FName)
SELECT
rid
,LName
,ISNULL((CASE
WHEN fn.fnid%(cast(rand(checksum(newid()))*(@fncount+1) as int)+1) > 0
THEN (SELECT TOP(1) FName FROM #firstname WHERE fnID = fn.fnid%(cast(rand(checksum(newid()))*(@fncount+1) as int)+1))
+' & '
+(SELECT TOP(1) FName FROM #firstname WHERE fnID = fn.fnid%(cast(rand(checksum(newid()))*(@fncount+1) as int)+1))
ELSE FName
END),FName) AS FName
FROM
#randomFullname r
INNER JOIN #firstname fn
ON r.fnid=fn.fnid
INNER JOIN
#lastName ln ON r.lnid=ln.lnid
SELECT * FROM #NamesToUpdate ORDER BY rid
The 3 variations of SELECT queries:
SELECT
ROW_NUMBER() OVER (ORDER BY rid) AS RowID,
rid,
LName,
FName = RTRIM(SUBSTRING(FName,1,CHARINDEX('&',FName,1)-1))
FROM
#NamesToUpdate
WHERE
rid > 0
AND FName LIKE '%&%'
SELECT
ROW_NUMBER() OVER (ORDER BY rid) AS RowID,
rid,
LName,
FName = RTRIM(SUBSTRING(FName,1,CHARINDEX('&',FName,1)-1))
FROM
#NamesToUpdate
WHERE
rid > 0
AND CHARINDEX('&',FName) > 0
SELECT
RowID,
rid,
LName,
FName = RTRIM(SUBSTRING(FName,1,CHARINDEX('&',FName,1)-1))
FROM
(
SELECT
ROW_NUMBER() OVER (PARTITION BY r.rid ORDER BY r.rid) AS RowID,
r.rid,
r.LName,
r.FName
FROM
#NamesToUpdate r
CROSS APPLY
dbo.DelimitedSplit8k(r.FName,'&') dsk
WHERE
r.rid > 0
) r1
WHERE
RowID = 2
And UPDATE query versions:
UPDATE #NamesToUpdate
SET FName = RTRIM(SUBSTRING(FName,1,CHARINDEX('&',FName,1)-1))
WHERE
FName LIKE '%&%'
UPDATE #NamesToUpdate
SET FName = RTRIM(SUBSTRING(FName,1,CHARINDEX('&',FName,1)-1))
WHERE
CHARINDEX('&',FName) > 0
UPDATE #NamesToUpdate
SET FName = RTRIM(SUBSTRING(FName,1,CHARINDEX('&',FName,1)-1))
WHERE rid IN
(
SELECT
rid
FROM
(
SELECT
ROW_NUMBER() OVER (PARTITION BY r.rid ORDER BY r.rid) AS RowID,
r.rid,
r.LName,
r.FName
FROM
#NamesToUpdate r
CROSS APPLY
dbo.DelimitedSplit8k(r.FName,'&') dsk
WHERE
r.rid > 0
) r1
WHERE
RowID = 2
)