I Know C#, I Want To Learn How I Write Scripts For Database Migration.

i found that code. but i does not understand the code.


public string GetTableScript(string TableName, string ConnectionString)
{
string Script = "";

string Sql = "declare @table varchar(100)" + Environment.NewLine +
"set @table = '" + TableName + "' " + Environment.NewLine +
//"-- set table name here" +
"declare @sql table(s varchar(1000), id int identity)" + Environment.NewLine +
" " + Environment.NewLine +
//"-- create statement" +
"insert into @sql(s) values ('create table [' + @table + '] (')" + Environment.NewLine +
" " + Environment.NewLine +
//"-- column list" +
"insert into @sql(s)" + Environment.NewLine +
"select " + Environment.NewLine +
" ' ['+column_name+'] ' + " + Environment.NewLine +
" data_type + coalesce('('+cast(character_maximum_length as varchar)+')','') +
' ' +" + Environment.NewLine +
" case when exists ( " + Environment.NewLine +
" select id from syscolumns" + Environment.NewLine +
" where object_name(id)=@table" + Environment.NewLine +
" and name=column_name" + Environment.NewLine +
" and columnproperty(id,name,'IsIdentity') = 1 " + Environment.NewLine +
" ) then" + Environment.NewLine +
" 'IDENTITY(' + " + Environment.NewLine +
" cast(ident_seed(@table) as varchar) + ',' + " + Environment.NewLine +
" cast(ident_incr(@table) as varchar) + ')'" + Environment.NewLine +
" else ''" + Environment.NewLine +
" end + ' ' +" + Environment.NewLine +
" ( case when IS_NULLABLE = 'No' then 'NOT ' else '' end ) + 'NULL ' + " + Environment.NewLine +
" coalesce('DEFAULT '+COLUMN_DEFAULT,'') + ','" + Environment.NewLine +
" " + Environment.NewLine +
" from information_schema.columns where table_name = @table" + Environment.NewLine +
" order by ordinal_position" + Environment.NewLine +
" " + Environment.NewLine +
//"-- primary key" +
"declare @pkname varchar(100)" + Environment.NewLine +
"select @pkname = constraint_name from information_schema.table_constraints" + Environment.NewLine +
"where table_name = @table and constraint_type='PRIMARY KEY'" + Environment.NewLine +
" " + Environment.NewLine +
"if ( @pkname is not null ) begin" + Environment.NewLine +
" insert into @sql(s) values(' PRIMARY KEY (')" + Environment.NewLine +
" insert into @sql(s)" + Environment.NewLine +
" select ' ['+COLUMN_NAME+'],' from information_schema.key_column_usage" + Environment.NewLine +
" where constraint_name = @pkname" + Environment.NewLine +
" order by ordinal_position" + Environment.NewLine +
//" -- remove trailing comma" +
" update @sql set s=left(s,len(s)-1) where id=@@identity" + Environment.NewLine +
" insert into @sql(s) values (' )')" + Environment.NewLine +
"end" + Environment.NewLine +
"else begin" + Environment.NewLine +
//" -- remove trailing comma" +
" update @sql set s=left(s,len(s)-1) where id=@@identity" + Environment.NewLine +
"end" + Environment.NewLine +
" " + Environment.NewLine +
"-- closing bracket" + Environment.NewLine +
"insert into @sql(s) values( ')' )" + Environment.NewLine +
" " + Environment.NewLine +
//"-- result!" +
"select s from @sql order by id";

DataTable dt = GetTableData(Sql, ConnectionString);
foreach (DataRow row in dt.Rows)
{
Script += row[0].ToString() + Environment.NewLine;
}

return Script;
}