导读：Redis是一个高性能的键值存储数据库，支持多种数据结构和丰富的操作命令。在使用Redis时，我们经常需要查询当前数据库中有多少个key，并进行相应的操作。本文将介绍如何查询Redis中的数据库数量。
1. 使用INFO命令
INFO命令可以获取Redis服务器的各种信息，包括数据库数量。具体操作步骤如下：
（1）连接Redis服务器
$ redis-cli
（2）发送INFO命令
127.0.0.1:6379> INFO
（3）查找databases字段
# Server
redis_version:6.2.5
redis_git_sha1:00000000
redis_git_dirty:0
redis_build_id:0c7f4a3b8ff8e1e8
redis_mode:standalone
os:Linux 4.19.128-microsoft-standard x86_64
arch_bits:64
multiplexing_api:epoll
atomicvar_api:atomic-builtin
gcc_version:9.3.0
process_id:466
run_id:a0a3dd9f7b2f8b96f7a7dc9edca5c9b04b9f1f4d
tcp_port:6379
uptime_in_seconds:5347
uptime_in_days:0
hz:10
configured_hz:10
lru_clock:2810972
executable:/usr/local/bin/redis-server
config_file:
# Clients
connected_clients:1
client_recent_max_input_buffer:2
client_recent_max_output_buffer:0
blocked_clients:0
# Memory
used_memory:854896
used_memory_human:834.94K
used_memory_rss:4194304
used_memory_rss_human:4.00M
used_memory_peak:855056
used_memory_peak_human:835.08K
used_memory_peak_perc:99.98%
used_memory_overhead:841896
used_memory_startup:786064
used_memory_dataset:13000
used_memory_dataset_perc:20.01%
allocator_allocated:1032192
allocator_active:2097152
allocator_resident:3145728
total_system_memory:16777216
total_system_memory_human:16.00M
used_memory_lua:37888
used_memory_lua_human:37.00K
used_memory_scripts:0
used_memory_scripts_human:0B
number_of_cached_scripts:0
maxmemory:0
maxmemory_human:0B
maxmemory_policy:noeviction
allocator_frag_ratio:2.03
allocator_frag_bytes:1064960
allocator_rss_ratio:1.50
allocator_rss_bytes:1048576
rss_overhead_ratio:1.33
rss_overhead_bytes:1048576
mem_fragmentation_ratio:5.30
mem_fragmentation_bytes:3340064
mem_not_counted_for_evict:0
mem_replication_backlog:0
mem_clients_slaves:0
mem_clients_normal:0
mem_aof_buffer:0
mem_allocator:jemalloc-5.2.1
active_defrag_running:0
lazyfree_pending_objects:0
# Persistence
loading:0
rdb_changes_since_last_save:0
rdb_bgsave_in_progress:0
rdb_last_save_time:1631381781
rdb_last_bgsave_status:ok
rdb_last_bgsave_time_sec:0
rdb_current_bgsave_time_sec:-1
rdb_last_cow_size:0
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
aof_last_write_status:ok
aof_last_cow_size:0
# Stats
total_connections_received:3
total_commands_processed:8
instantaneous_ops_per_sec:0
total_net_input_bytes:272
total_net_output_bytes:1723
instantaneous_input_kbps:0.00
instantaneous_output_kbps:0.00
rejected_connections:0
sync_full:0
sync_partial_ok:0
sync_partial_err:0
expired_keys:0
expired_stale_perc:0.00
expired_time_cap_reached_count:0
evicted_keys:0
keyspace_hits:0
keyspace_misses:0
pubsub_channels:0
pubsub_patterns:0
latest_fork_usec:0
migrate_cached_sockets:0
slave_expires_tracked_keys:0
active_defrag_hits:0
active_defrag_misses:0
active_defrag_key_hits:0
active_defrag_key_misses:0
# Replication
role:master
connected_slaves:0
master_replid:ead9c7c5f6d76e4b0c6d3e2b7b535fdd6b380a4b
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:0
second_repl_offset:-1
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
# CPU
used_cpu_sys:0.000000
used_cpu_user:0.000000
used_cpu_sys_children:0.000000
used_cpu_user_children:0.000000
# Cluster
cluster_enabled:0
# Keyspace
db0:keys=1,expires=0,avg_ttl=0
可以看到，该Redis服务器中有1个数据库。
2. 使用CONFIG命令
CONFIG命令可以获取Redis服务器的配置信息，
