MongoDB(三) 常用操作

MongoDB 常用操作

# 查看索引是否存在
> db.boundary.ensureIndex({ "geometry" : "2dsphere" } )
{
	"createdCollectionAutomatically" : false,
	"numIndexesBefore" : 2,
	"numIndexesAfter" : 2,
	"note" : "all indexes already exist",
	"ok" : 1
}

# 删除索引
> db.boundary.dropIndex({ "geometry" : "2dsphere" })
{ "nIndexesWas" : 2, "ok" : 1 }

# 查询某一字段是否存在
> db.boundary.find( { "geometry": { $exists: true } } ).count()
54

# 删除表中的某一字段
> db.boundary.update( {}, {$unset: {"geometry":""} }, {multi: true} )
WriteResult({ "nMatched" : 1971, "nUpserted" : 0, "nModified" : 54 })

# 创建索引
db.boundary.createIndex({ "geometry": "2dsphere" })