HBase get和scan命令：查询数据（附带实例）

HBase Shell 数据操作的命令如下表所示：

表：HBase Shell 数据操作的命令

命令	描述
put	添加一个值到单元格中
get	获取行、单元格数据
scan	扫描表数据
count	统计表中的逻辑行
delete	删除列族或列数据

HBase get命令

get 命令可以获取表中一行的数据，必须指定表名和行键。

例如，获取 Student 表中行键 001 的一行数据：


具体代码如下：

hbase(main):025:0> get 'Student','001'
COLUMN CELL
  Grades:BigData         timestamp = 1630071771468, value = 90
  Grades:Computer        timestamp = 1630071781218, value = 85
  Grades:Math            timestamp = 1630071788138, value = 70
  StuInfo:Age            timestamp = 1630071738515, value = 20
  StuInfo:Sex            timestamp = 1630071747571, value = Male
1 row(s) in 0.0060 seconds

get 命令也可以根据指定的列族和列标识，获取一行中对应列族的数据或对应单元格的数据。如获取 Student 表中行键 001 的学生姓名及两个版本的学生信息，具体操作如下：

hbase(main):032:0> get 'Student','001','StuInfo:Name'
  COLUMN                 CELL
  StuInfo:Name           timestamp = 1630072022705, value = Tom
1 row(s) in 0.0040 seconds
hbase(main):033:0> get 'Student','001','StuInfo'
  COLUMN                 CELL
  StuInfo:Age            timestamp = 1630071738515, value = 20
  StuInfo:Name           timestamp = 1630072022705, value = Tom
  StuInfo:Sex            timestamp = 1630071747571, value = Male
1 row(s) in 0.0040 seconds

HBase scan命令

查询数据还经常使用 scan 命令。scan 命令可以扫描全表数据，也可以扫描加入一些限定条件的表中数据，使用方式具体如下：

# 查询Student全表数据，获取所有的行
hbase(main):034:0> scan 'Student'
  ROW            COLUMN + CELL
  001            column = Grades:BigData, timestamp = 1630071771468, value = 90
  001            column = Grades:Computer, timestamp = 1630071781218, value = 85
  001            column = Grades:Math, timestamp = 1630071788138, value = 70
  001            column = StuInfo:Age, timestamp = 1630071738515, value = 20
  001            column = StuInfo:Name, timestamp = 1630072022705, value = Tom
  001            column = StuInfo:Sex, timestamp = 1630071747571, value = Male
1 row(s) in 0.0140 seconds
# 查询Student表StuInfo列族的所有数据
hbase(main):035:0> scan 'Student',{COLUMN => ＂StuInfo＂}
  ROW            COLUMN + CELL
  001            column = StuInfo:Age, timestamp = 1630071738515, value = 20
  001            column = StuInfo:Name, timestamp = 1630072022705, value = Tom
  001            column = StuInfo:Sex, timestamp = 1630071747571, value = Male
1 row(s) in 0.0050 seconds
# 查询StuInfo:Name列的所有数据
hbase(main):036:0> scan 'Student',{COLUMN => ＂StuInfo:Name＂}
  ROW            COLUMN + CELL
  001            column = StuInfo:Name, timestamp = 1630072022705, value = Tom
1 row(s) in 0.0050 seconds
# 限定查询的数据条数
hbase(main):037:0> scan 'Student',{LIMIT => 1}
  ROW            COLUMN + CELL
  001            column = Grades:BigData, timestamp = 1630071771468, value = 90
  001            column = Grades:Computer, timestamp = 1630071781218, value = 85
  001            column = Grades:Math, timestamp = 1630071788138, value = 70
  001            column = StuInfo:Age, timestamp = 1630071738515, value = 20
  001            column = StuInfo:Name, timestamp = 1630072022705, value = Tom
  001 column = StuInfo:Sex, timestamp = 1630071747571, value = Male
1 row(s) in 0.0080 seconds
# 限定行键的范围，只包含STARTROW，不包含ENDROW
hbase(main):039:0> scan 'Student',{STARTROW => '001',ENDROW => '002'}
  ROW            COLUMN + CELL
  001            column = Grades:BigData, timestamp = 1630071771468, value = 90
  001            column = Grades:Computer, timestamp = 1630071781218, value = 85
  001            column = Grades:Math, timestamp = 1630071788138, value = 70
  001            column = StuInfo:Age, timestamp = 1630071738515, value = 20
  001            column = StuInfo:Name, timestamp = 1630072022705, value = Tom
  001            column = StuInfo:Sex, timestamp = 1630071747571, value = Male
1 row(s) in 0.0120 seconds

统计一个 HBase 数据表中有多少行时可以使用 count 命令，该命令会进行全表扫描，但不统计相同的行键和标记“删除”的数据行的数量。当数据量大时，该命令耗费的时间将比较长。