这个SQL语句哪里错了? - .NET技术 / ASP.NET

这个SQL语句哪里错了?
 string alterColSQL = "alter table " + tableName + " add column " + name + " varchar(20) " + meaning + " varchar(100) " + type + " varchar(50) " + dataSource + " varchar(50) ";
目的是在一个表中加几个字段,哪里出问题了?

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string alterColSQL = "alter table " + tableName + " add column " + name + " varchar(20) "+";alter table " + tableName + " add column " + meaning + " varchar(100) "+";alter table " + tableName + " add column " + name + " varchar(50) "+";alter table " + tableName + " add column " + name + " varchar(50) "

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string alterColSQL = "alter table " + tableName + " add column " + name + " varchar(20), " + meaning + " varchar(100), " + type + " varchar(50), " + dataSource + " varchar(50) ";

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SQL code:

alter table tableName add ColumnName int

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alter table dbo.BJ_JHLX add test1 varchar(20) not null default 0,test2 varchar(30) not null default 0//不允许为空，默认值
alter table dbo.BJ_JHLX add test1 varchar(20) null,test2 varchar(30) null//允许为空

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数据库错误：关键字 'column' 附近有语法错误。 
说明: