查询当前数据库中所有用户表中哪些字段包含某个字符串 那个语句中 sys.extended_properties 是什么意思？

FROM syscolumns a
left join systypes b on a.xtype=b.xusertype
inner join sysobjects d on a.id=d.id and d.xtype='U' and d.name<>'dtproperties'
left join syscomments e on a.cdefault=e.id
left join sys.extended_properties g on a.id=g.major_id AND a.colid = g.minor_id
--where d.name in ('Contact','StockBmps','AddressType')---查询具体的表，注释掉后就是查询整个数据库了
order by a.id,a.colorder

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