mysql>use zabbix;
显示zabbix数据库中的表大小；
mysql>SELECT table_name AS "Tables", round(((data_length + index_length) / 1024 / 1024), 2) "Size in MB" FROM information_schema.TABLES WHERE table_schema = 'zabbix' ORDER BY (data_length + index_length) DESC;
+----------------------------+------------+
| Tables | Size in MB |
+----------------------------+------------+
| history_uint | 887.00 |
| history | 674.05 |
| trends_uint | 22.38 |
| trends | 19.39 |
| events | 4.55 |
| images | 1.53 |
| items | 0.72 |
| history_str | 0.33 |
| alerts | 0.25 |
| items_applications | 0.23 |
| profiles | 0.22 |
| auditlog | 0.17 |
| triggers | 0.14 |
| graphs | 0.13 |
| hosts | 0.11 |
| graphs_items | 0.11 |
| sysmaps_elements | 0.09 |
| item_discovery | 0.09 |
| sysmaps | 0.08 |
| httptest | 0.08 |
| functions | 0.08 |
| sysmaps_links | 0.06 |
| acknowledges | 0.06 |
| group_prototype | 0.06 |
| scripts | 0.06 |
| actions | 0.06 |
| slideshows | 0.05 |
| config | 0.05 |
| item_application_prototype | 0.05 |
| slideshow_usrgrp | 0.05 |
| sysmaps_link_triggers | 0.05 |
| optemplate | 0.05 |
| hosts_templates | 0.05 |
| slideshow_user | 0.05 |
| media | 0.05 |
| opmessage_usr | 0.05 |
| hosts_groups | 0.05 |
| users_groups | 0.05 |
| interface | 0.05 |
| slides | 0.05 |
| screens | 0.05 |
| dservices | 0.05 |
| opmessage_grp | 0.05 |
| maintenances_windows | 0.05 |
| screen_usrgrp | 0.05 |
| sysmap_usrgrp | 0.05 |
| drules | 0.05 |
| maintenances_hosts | 0.05 |
| screen_user | 0.05 |
| icon_mapping | 0.05 |
| opgroup | 0.05 |
| rights | 0.05 |
| services_links | 0.05 |
| maintenances_groups | 0.05 |
| application_template | 0.05 |
| host_discovery | 0.05 |
| icon_map | 0.05 |
| trigger_depends | 0.05 |
| application_prototype | 0.05 |
| httptestitem | 0.05 |
| sysmap_user | 0.05 |
| service_alarms | 0.05 |
| application_discovery | 0.05 |
| history_text | 0.05 |
| opcommand_hst | 0.05 |
| httpstepitem | 0.05 |
| opcommand_grp | 0.05 |
| httpstep | 0.03 |
| opcommand | 0.03 |
| expressions | 0.03 |
| media_type | 0.03 |
| conditions | 0.03 |
| usrgrp | 0.03 |
| groups | 0.03 |
| interface_discovery | 0.03 |
| autoreg_host | 0.03 |
| escalations | 0.03 |
| mappings | 0.03 |
| group_discovery | 0.03 |
| auditlog_details | 0.03 |
| users | 0.03 |
| sessions | 0.03 |
| opmessage | 0.03 |
| hostmacro | 0.03 |
| services_times | 0.03 |
| dhosts | 0.03 |
| applications | 0.03 |
| trigger_discovery | 0.03 |
| graph_theme | 0.03 |
| operations | 0.03 |
| services | 0.03 |
| graph_discovery | 0.03 |
| regexps | 0.03 |
| opconditions | 0.03 |
| sysmap_url | 0.03 |
| valuemaps | 0.03 |
| dchecks | 0.03 |
| sysmap_element_url | 0.03 |
| screens_items | 0.03 |
| item_condition | 0.03 |
| housekeeper | 0.02 |
| ids | 0.02 |
| opinventory | 0.02 |
| host_inventory | 0.02 |
| maintenances | 0.02 |
| globalvars | 0.02 |
| proxy_history | 0.02 |
| globalmacro | 0.02 |
| proxy_dhistory | 0.02 |
| timeperiods | 0.02 |
| proxy_autoreg_host | 0.02 |
| dbversion | 0.02 |
| history_log | 0.02 |
+----------------------------+------------+
113 rows in set (0.14 sec)
描述表结构：
mysql>desc history_uint;
+--------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+-------+
| itemid | bigint(20) unsigned | NO | MUL | NULL | |
| clock | int(11) | NO | | 0 | |
| value | bigint(20) unsigned | NO | | 0 | |
| ns | int(11) | NO | | 0 | |
+--------+---------------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
清除历史缓存：
mysql> truncate table history;
Query OK, 0 rows affected (0.15 sec)
mysql> truncate table history_uint;
Query OK, 0 rows affected (0.13 sec)
有时候我们会需要清除一个表格中的所有资料。要达到者个目的，一种方式是我们在 SQL DROP 那一页 看到 的 DROP TABLE 指令。不过这样整个表格就消失，而无法再被用了。另一种方式就是运用 TRUNCATE TABLE 的指令。在这个指令之下，表格中的资料会完全消失，可是表格本身会继续存在。 TRUNCATE TABLE 的语法为下：
TRUNCATE TABLE "表格名";
所以，我们如果要清除在 SQL Create Table 那一页建立的顾客表格之内的资料，我们就打入：
TRUNCATE TABLE Customer;
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