MySQL是一款非常流行的開源數(shù)據(jù)庫(kù)管理系統(tǒng)。在存儲(chǔ)大量數(shù)據(jù)時(shí),為了更好地管理數(shù)據(jù)和加速查詢,通常需要使用分表技術(shù)。
下面介紹三種常用的MySQL分表方案:
1. 按照ID范圍分表
CREATE TABLE sharding_table_0 ( id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT, user_id BIGINT(20) UNSIGNED NOT NULL, name VARCHAR(50), PRIMARY KEY (id) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci; CREATE TABLE sharding_table_1 ( id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT, user_id BIGINT(20) UNSIGNED NOT NULL, name VARCHAR(50), PRIMARY KEY (id) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
在此方案中,按照ID范圍,將表分為多個(gè)子表,例如ID為0-99999的數(shù)據(jù)分到sharding_table_0中,ID為100000-199999的數(shù)據(jù)分到sharding_table_1中。當(dāng)查詢數(shù)據(jù)時(shí),需要先根據(jù)ID范圍確定子表,再查詢相應(yīng)的子表,最終將結(jié)果合并。
2. 按照Hash散列分表
CREATE TABLE sharding_table_0 ( id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT, user_id BIGINT(20) UNSIGNED NOT NULL, name VARCHAR(50), PRIMARY KEY (id) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci; CREATE TABLE sharding_table_1 ( id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT, user_id BIGINT(20) UNSIGNED NOT NULL, name VARCHAR(50), PRIMARY KEY (id) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
在此方案中,采用哈希函數(shù)對(duì)數(shù)據(jù)進(jìn)行散列,根據(jù)散列結(jié)果將數(shù)據(jù)分配到多個(gè)表中。例如對(duì)user_id進(jìn)行哈希散列后,散列結(jié)果為0的數(shù)據(jù)分到sharding_table_0中,散列結(jié)果為1的數(shù)據(jù)分到sharding_table_1中。當(dāng)查詢數(shù)據(jù)時(shí),需要根據(jù)哈希函數(shù)計(jì)算出相應(yīng)的子表,再查詢相應(yīng)的子表,最終將結(jié)果合并。
3. 按照時(shí)間分表
CREATE TABLE sharding_table_201901 ( id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT, user_id BIGINT(20) UNSIGNED NOT NULL, name VARCHAR(50), PRIMARY KEY (id) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci; CREATE TABLE sharding_table_201902 ( id BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT, user_id BIGINT(20) UNSIGNED NOT NULL, name VARCHAR(50), PRIMARY KEY (id) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
在此方案中,根據(jù)時(shí)間對(duì)數(shù)據(jù)進(jìn)行分表。例如,2019年1月的數(shù)據(jù)存儲(chǔ)在sharding_table_201901中,2019年2月的數(shù)據(jù)存儲(chǔ)在sharding_table_201902中。當(dāng)查詢數(shù)據(jù)時(shí),需要先根據(jù)時(shí)間確定子表,再查詢相應(yīng)的子表,最終將結(jié)果合并。