How to split string and save into an array in T-SQ

问题:

I am writing a cursor to populate data in new table from main table which contains data in below manner

Item    Colors
Shirt    Red,Blue,Green,Yellow

I want to populate new Table data by fetching the Item and then adding it in row, according to each color it contains

Item    Color
Shirt    Red
Shirt    Blue
Shirt    Green
Shirt    Yellow

I am stuck in how to

1) Delimate/Split "Colors" string 2) To save it in an array 3) To use it in cursor

as I am going to use Nested cursor for this purpose.

回答1:

Using Sql Server 2005+ and the XML datatype, you can have a look at the following

DECLARE @Table TABLE(
        Item VARCHAR(250),
        Colors VARCHAR(250)
)

INSERT INTO @Table SELECT 'Shirt','Red,Blue,Green,Yellow'
INSERT INTO @Table SELECT 'Pants','Black,White'


;WITH Vals AS (
        SELECT  Item,
                CAST('<d>' + REPLACE(Colors, ',', '</d><d>') + '</d>' AS XML) XmlColumn
        FROM    @Table
)
SELECT  Vals.Item,
        C.value('.','varchar(max)') ColumnValue
FROM    Vals
CROSS APPLY Vals.XmlColumn.nodes('/d') AS T(C)

回答2:

The article Faking Arrays in Transact SQL details SEVERAL techniques to solve this problem, ranging from using the PARSENAME() function (limit to 5 items) to writing CLR functions.

The XML answer is one of the detailed techniques that can be chosen to a specific scenario.

Combining some of the tips, I solved my string split problem like this:

SET NOCOUNT ON;

DECLARE @p NVARCHAR(1000), @len INT;
SET @p = N'value 1,value 2,value 3,value 4,etc';
SET @p = ',' + @p + ',';
SET @len = LEN(@p);

-- Remove this table variable creation if you have a permanent enumeration table
DECLARE @nums TABLE (n int);
INSERT INTO @nums (n)
    SELECT A.n FROM 
    (SELECT TOP 1000 ROW_NUMBER() OVER (ORDER BY TableKey) as n FROM dbo.Table) A
    WHERE A.n BETWEEN 1 AND @len;

SELECT SUBSTRING(@p , n + 1, CHARINDEX( ',', @p, n + 1 ) - n - 1 ) AS "value"
    FROM @nums
    WHERE SUBSTRING( @p, n, 1 ) = ',' AND n < @len;

Note that, considering 1000 your string length limit, you must have a table with 1000 or more rows (dbo.Table on the sample tsql) to create the table variable @nums of this sample. On the article, they have a permanent enumeration table.

回答3:

Starting from SQL Server 2016 it could be done with OPENJSON and JSON_VALUE functions.

回答4:

I just accomplished something like this to create staging tables to replicate the source tables using the INFORMATION_SCHEMA views on a linked server. But this is a modified version to create the results you are look for. Just remember to remove the last two characters from the Colors column when displaying it.

SELECT
    t.Item
    , (
        SELECT 
            x.Color + ', ' AS [data()]
        FROM 
            Items x
        WHERE 
            x.Item = t.Item
        FOR XML PATH(''), TYPE
    ).value('.', 'varchar(max)') AS Colors
FROM 
    Items t
GROUP BY 
    t.Item