zadd command fail

[xiaofangzhen]

redis 127.0.0.1:6501> zscore rankByPk2 505219
"0"
redis 127.0.0.1:6501> zscore rankByPk2 526372
"0"
redis 127.0.0.1:6501> zadd rankByPk2 526372 1
(integer) 1
redis 127.0.0.1:6501> zscore rankByPk2 526372
"0"
redis 127.0.0.1:6501>

what is wrong ?after i set 526372 as 1,but it is still 0.

redis 127.0.0.1:6501> info

Server

redis_version:2.6.16
redis_git_sha1:00000000
redis_git_dirty:0
redis_mode:standalone
os:Linux 2.6.32-220.el6.x86_64 x86_64
arch_bits:64
multiplexing_api:epoll
gcc_version:4.4.7
process_id:16580
run_id:2355278610ca9a098d170852902ebc06ccb3f866
tcp_port:6501
uptime_in_seconds:3907964
uptime_in_days:45
hz:10
lru_clock:2089014

Clients

connected_clients:2
client_longest_output_list:0
client_biggest_input_buf:0
blocked_clients:0

Memory

used_memory:2143946992
used_memory_human:2.00G
used_memory_rss:2262351872
used_memory_peak:2172920408
used_memory_peak_human:2.02G
used_memory_lua:31744
mem_fragmentation_ratio:1.06
mem_allocator:jemalloc-3.2.0

Persistence

loading:0
rdb_changes_since_last_save:4846
rdb_bgsave_in_progress:0
rdb_last_save_time:1425964888
rdb_last_bgsave_status:ok
rdb_last_bgsave_time_sec:8
rdb_current_bgsave_time_sec:-1
aof_enabled:0
aof_rewrite_in_progress:0
aof_rewrite_scheduled:0
aof_last_rewrite_time_sec:-1
aof_current_rewrite_time_sec:-1
aof_last_bgrewrite_status:ok

Stats

total_connections_received:104736
total_commands_processed:22488383
instantaneous_ops_per_sec:0
rejected_connections:0
expired_keys:7
evicted_keys:0
keyspace_hits:4852525
keyspace_misses:1420
pubsub_channels:0
pubsub_patterns:0
latest_fork_usec:2114

Replication

role:master
connected_slaves:0

CPU

used_cpu_sys:1086.30
used_cpu_user:627.76
used_cpu_sys_children:259.09
used_cpu_user_children:1400.49

Keyspace

db0:keys=325371,expires=1,avg_ttl=58403939
redis 127.0.0.1:6501>