我的选择查询非常慢，我需要深入了解如何改进它

Question

我有一个用于检索表数据的查询。当返回的行数超过3-4时，查询速度非常慢，我不明白为什么。

这是我的查询：

select 
        ig.id,
        ig.username,
        ig.created,
        ig.is_completed,
        ig.user_id,
        ig.is_error,
        ig.last_appeal_process_update,
        (unix_timestamp() - ig.created) as time_running,
        ig.is_deleted,
        ap.id as appealprocessid,
        (case 
            when ap.id is null then 0
            when ap.id is not null then ap.status
        end
        ) as current_status,
        ( select count(*) from appeal_process where ig_account_id = ig.id)
        as total_appeals
        from instagram_accounts ig
        left join appeal_process ap on ig.id = ap.ig_account_id
        where 
        (ig.username like CONCAT('%',?,'%') or ig.id like CONCAT('%',?,'%') or ig.username like CONCAT('%',?,'%')) and 
        ig.user_id = ? and is_deleted = 0 and 
        (
            ap.id is null or
            ap.id = ( -- WE SELECT ONLY THE LATEST APPEAL PROCESS
                select max(id) from appeal_process tmp where tmp.ig_account_id = ig.id limit 1
            )   
        )
        order by ig.username asc
        limit ?,?

编辑

这是EXPLAIN查询（尽管我不知道如何阅读）enter image description here

这是instagram_accounts的SHOW CREATE TABLE：enter image description here

这是appeal_process的SHOW CREATE TABLE：enter image description here

Answer 1

[您的问题很可能是由于缺少索引而引起的，有必要对WHERE和JOIN子句中使用的字段建立索引。

为这些字段中的每个字段创建索引：

ig_account_id

ig.id

ig.username

is_deleted

ig.user_id

tmp.ig_account_id