Why does mysql obviously enable the cache but cannot be used?

Step 1: SHOWVARIABLESLIKE & #39; % cache % & #39; result: have_query_cacheYES Step 2: success; Step 3: SHOWSTATUSLIKE & #39; % Qcache % & #39 ;; qcache_free_blocks0Qcache_free_memory0Qcache_hits0Qcache_inser mysql cache

Step 1: show variables like '% cache % ';

Result: have_query_cache YES.

Step 2: SELECT SQL _CACHE cr_name FROM t_course t WHERE t. course_id = 365;

Step 3: show status like '% Qcache % ';
Qcache_free_blocks 0
Qcache_free_memory 0
Qcache_hits 0
Qcache_inserts 0
Qcache_lowmem_prunes 0
Qcache_not_cached 0
Qcache_queries_in_cache 0
Qcache_total_blocks 0

Thank you!
I can't find any places to disable caching.