求Sql 语句的写法 - MS-SQL Server / 疑难问题

表名 : tb1
字段名称: ID a
字段值 : 1 10667766*X06*KYG08B01L18XU01*V4_10667766*X06*KYG08B01L18XU01*V4
2 10667766*X06*KYG01TSTSHELU01_10667766*A53*KYG01TSTSHELU01_10667766*X06*KYG01TSTSHELU01*V4
3 10668001*2KY*KYM01B01L18XU01*V4
4 1062376664*4*KYG08B01L18XU01*V4_1062376664*4*KYG08B01L18XU01*V4


怎么把上表变成如下所示:

ID a1 a2 a3
1 10667766*X06*KYG08B01L18XU01*V4 10667766*X06*KYG08B01L18XU01*V4
2 10667766*X06*KYG01TSTSHELU01 10667766*A53*KYG01TSTSHELU01 10667766*X06*KYG01TSTSHELU01*V4
3 10668001*2KY*KYM01B01L18XU01*V4
4 1062376664*4*KYG08B01L18XU01 KYG08B01L18XU01*V4 1062376664*4*KYG08B01L18XU01*V4

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Don't understand the logic. You need to provide more information as to how you arrive from the original table to the output you provided.

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SQL code:
－－动态SQL：

--> 生成测试数据表: [tb]
IF OBJECT_ID('[tb]') IS NOT NULL
DROP TABLE [tb]
GO
CREATE TABLE [tb] ([ID] [int],[a] [nvarchar](90))
INSERT INTO [tb]
SELECT '1','10667766*X06*KYG08B01L18XU01*V4_10667766*X06*KYG08B01L18XU01*V4' UNION ALL
SELECT '2','10667766*X06*KYG01TSTSHELU01_10667766*A53*KYG01TSTSHELU01_10667766*X06*KYG01TSTSHELU01*V4' UNION ALL
SELECT '3','10668