今天发现一个问题，where条件的列上明明有索引，但是执行计划还是走全表扫描
mysql> explain select task_id FROM mostop_xiaodai_collection_call_auto WHERE task_id = 433423882127424 AND task_data_id = 27739131157286912;
+----+-------------+-------------------------------------+------------+------+------------------------------+------+---------+------+---------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------------------------------------+------------+------+------------------------------+------+---------+------+---------+----------+-------------+
| 1 | SIMPLE | mostop_xiaodai_collection_call_auto | NULL | ALL | IDX_task_id,IDX_task_data_id | NULL | NULL | NULL | 3101134 | 1.00 | Using where |
+----+-------------+-------------------------------------+------------+------+------------------------------+------+---------+------+---------+----------+-------------+
1 row in set, 5 warnings (0.00 sec)查看表结构
mysql> show create table mostop_xiaodai_collection_call_auto\G
*************************** 1. row ***************************
Table: mostop_xiaodai_collection_call_auto
Create Table: CREATE TABLE `mostop_xiaodai_collection_call_auto` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '编号',
`agentid` int(10) unsigned NOT NULL COMMENT '渠道 ID',
`loan_id` bigint(20) unsigned NOT NULL DEFAULT '0' COMMENT '借款 ID',
`user_id` bigint(20) unsigned NOT NULL COMMENT '借款人 ID',
`call_mobile` varchar(20) NOT NULL COMMENT '手机号',
`call_name` varchar(20) NOT NULL COMMENT '名称',
`call_sex` varchar(20) NOT NULL COMMENT '性别',
`call_due_date` date NOT NULL COMMENT '应还日期',
`call_overdue_day` int(10) NOT NULL COMMENT '逾期天数（负数为贷前催告的天数）',
`call_talking_type` varchar(50) NOT NULL COMMENT '话术 (A：贷前7天的提醒话术 B：贷前3天的话术 C：贷前3天的话术 D：贷前1天的话术 Ps：若话术为空，则使用的是大唐的话术，其余类似due_one之类的均已废弃)',
`call_platform_name` varchar(100) NOT NULL COMMENT '平台名称',
`third_party_system` tinyint(3) unsigned NOT NULL COMMENT '第三方IVR系统，1 = 百可录(暂停使用)，2 = 大唐，3 = 云电帮(暂停使用), 4 = 科大讯飞, 5 = 基立讯，99 = 决策引擎测试',
`send_time` datetime DEFAULT NULL COMMENT '发送时间',
`send_status` tinyint(3) unsigned NOT NULL DEFAULT '0' COMMENT '发送状态，0 = 未发送，1 = 发送成功，2 = 发送失败',
`send_result` tinyint(3) DEFAULT '0' COMMENT 'IVR结果( 0 = 代表无效接听，或者未接听，1 = 有效接听，已通知用户)',
`talking_time` int(10) NOT NULL DEFAULT '0' COMMENT '通话时长',
`task_id` varchar(32) NOT NULL DEFAULT '0' COMMENT '外呼任务ID (只为科大讯飞服务)',
`task_data_id` varchar(32) NOT NULL DEFAULT '0' COMMENT '外呼任务二级ID (只为科大讯飞服务)',
`resend_num` tinyint(3) unsigned NOT NULL DEFAULT '0' COMMENT '重发次数',
`receive_time` datetime DEFAULT NULL COMMENT '接收时间',
`receive_content` text COMMENT '接收内容',
`unique_tab` varchar(100) DEFAULT NULL COMMENT '唯一标识',
`created_at` int(10) unsigned NOT NULL DEFAULT '0' COMMENT '创建时间',
`updated_at` int(10) unsigned NOT NULL DEFAULT '0' COMMENT '更新时间',
PRIMARY KEY (`id`),
KEY `loan_id` (`agentid`,`loan_id`),
KEY `send_result` (`call_mobile`,`send_time`),
KEY `receive_time` (`receive_time`),
KEY `IDX_task_id` (`task_id`),
KEY `IDX_task_data_id` (`task_data_id`)
) ENGINE=InnoDB AUTO_INCREMENT=5292233 DEFAULT CHARSET=utf8 COMMENT='催收自动通话表'
1 row in set (0.00 sec)查看warnings
因为这两列为字符串类型 ，但是SQL中并没有加引号！！
`task_id` varchar(32)
`task_data_id` varchar(32)加上引号后查看执行计划
mysql> explain select task_id FROM mostop_xiaodai_collection_call_auto WHERE task_id = '433423882127424' AND task_data_id =' 27739131157286912';
+----+-------------+-------------------------------------+------------+------+------------------------------+------------------+---------+-------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------------------------------------+------------+------+------------------------------+------------------+---------+-------+------+----------+-------------+
| 1 | SIMPLE | mostop_xiaodai_collection_call_auto | NULL | ref | IDX_task_id,IDX_task_data_id | IDX_task_data_id | 98 | const | 1 | 5.00 | Using where |
+----+-------------+-------------------------------------+------------+------+------------------------------+------------------+---------+-------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
