SQL将值拆分为多个行
我有桌子：
id | name 1 | a,b,c 2 | b 我想要这样的输出：
id | name 1 | a 1 | b 1 | c 2 | b
如果您可以创build一个数字表，其中包含从1到最大字段的数字，您可以使用像这样的解决scheme：
select tablename.id, SUBSTRING_INDEX(SUBSTRING_INDEX(tablename.name, ',', numbers.n), ',', -1) name from numbers inner join tablename on CHAR_LENGTH(tablename.name) -CHAR_LENGTH(REPLACE(tablename.name, ',', ''))>=numbers.n-1 order by id, n
请看这里的小提琴。
如果你不能创build一个表，那么一个解决scheme可以是这样的：
select tablename.id, SUBSTRING_INDEX(SUBSTRING_INDEX(tablename.name, ',', numbers.n), ',', -1) name from (select 1 n union all select 2 union all select 3 union all select 4 union all select 5) numbers INNER JOIN tablename on CHAR_LENGTH(tablename.name) -CHAR_LENGTH(REPLACE(tablename.name, ',', ''))>=numbers.n-1 order by id, n
一个例子小提琴在这里 。
我从这里采取了更改列名称的参考。
DELIMITER $$ CREATE FUNCTION strSplit(x VARCHAR(65000), delim VARCHAR(12), pos INTEGER) RETURNS VARCHAR(65000) BEGIN DECLARE output VARCHAR(65000); SET output = REPLACE(SUBSTRING(SUBSTRING_INDEX(x, delim, pos) , LENGTH(SUBSTRING_INDEX(x, delim, pos - 1)) + 1) , delim , ''); IF output = '' THEN SET output = null; END IF; RETURN output; END $$ CREATE PROCEDURE BadTableToGoodTable() BEGIN DECLARE i INTEGER; SET i = 1; REPEAT INSERT INTO GoodTable (id, name) SELECT id, strSplit(name, ',', i) FROM BadTable WHERE strSplit(name, ',', i) IS NOT NULL; SET i = i + 1; UNTIL ROW_COUNT() = 0 END REPEAT; END $$ DELIMITER ;
我的变体：以表名，字段名和分隔符作为参数的存储过程。 灵感来自http://www.marcogoncalves.com/2011/03/mysql-split-column-string-into-rows/
delimiter $$ DROP PROCEDURE IF EXISTS split_value_into_multiple_rows $$ CREATE PROCEDURE split_value_into_multiple_rows(tablename VARCHAR(20), id_column VARCHAR(20), value_column VARCHAR(20), delim CHAR(1)) BEGIN DECLARE id INT DEFAULT 0; DECLARE value VARCHAR(255); DECLARE occurrences INT DEFAULT 0; DECLARE i INT DEFAULT 0; DECLARE splitted_value VARCHAR(255); DECLARE done INT DEFAULT 0; DECLARE cur CURSOR FOR SELECT tmp_table1.id, tmp_table1.value FROM \ tmp_table1 WHERE tmp_table1.value IS NOT NULL AND tmp_table1.value != ''; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; SET @expr = CONCAT('CREATE TEMPORARY TABLE tmp_table1 (id INT NOT NULL, value VARCHAR(255)) ENGINE=Memory SELECT ', id_column,' id, ', value_column,' value FROM ',tablename); PREPARE stmt FROM @expr; EXECUTE stmt; DEALLOCATE PREPARE stmt; DROP TEMPORARY TABLE IF EXISTS tmp_table2; CREATE TEMPORARY TABLE tmp_table2 (id INT NOT NULL, value VARCHAR(255) NOT NULL) ENGINE=Memory; OPEN cur; read_loop: LOOP FETCH cur INTO id, value; IF done THEN LEAVE read_loop; END IF; SET occurrences = (SELECT CHAR_LENGTH(value) - CHAR_LENGTH(REPLACE(value, delim, '')) + 1); SET i=1; WHILE i <= occurrences DO SET splitted_value = (SELECT TRIM(SUBSTRING_INDEX( SUBSTRING_INDEX(value, delim, i), delim, -1))); INSERT INTO tmp_table2 VALUES (id, splitted_value); SET i = i + 1; END WHILE; END LOOP; SELECT * FROM tmp_table2; CLOSE cur; DROP TEMPORARY TABLE tmp_table1; END; $$ delimiter ;
用法示例（标准化）：
CALL split_value_into_multiple_rows('my_contacts', 'contact_id', 'interests', ','); CREATE TABLE interests ( interest_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, interest VARCHAR(30) NOT NULL ) SELECT DISTINCT value interest FROM tmp_table2; CREATE TABLE contact_interest ( contact_id INT NOT NULL, interest_id INT NOT NULL, CONSTRAINT fk_contact_interest_my_contacts_contact_id FOREIGN KEY (contact_id) REFERENCES my_contacts (contact_id), CONSTRAINT fk_contact_interest_interests_interest_id FOREIGN KEY (interest_id) REFERENCES interests (interest_id) ) SELECT my_contacts.contact_id, interests.interest_id FROM my_contacts, tmp_table2, interests WHERE my_contacts.contact_id = tmp_table2.id AND interests.interest = tmp_table2.value;
CREATE PROCEDURE `getVal`() BEGIN declare r_len integer; declare r_id integer; declare r_val varchar(20); declare i integer; DECLARE found_row int(10); DECLARE row CURSOR FOR select length(replace(val,"|","")),id,val from split; create table x(id int,name varchar(20)); open row; select FOUND_ROWS() into found_row ; read_loop: LOOP IF found_row = 0 THEN LEAVE read_loop; END IF; set i = 1; FETCH row INTO r_len,r_id,r_val; label1: LOOP IF i <= r_len THEN insert into x values( r_id,SUBSTRING(replace(r_val,"|",""),i,1)); SET i = i + 1; ITERATE label1; END IF; LEAVE label1; END LOOP label1; set found_row = found_row - 1; END LOOP; close row; select * from x; drop table x; END
使用这个代码…
SELECT DISTINCT x.id, CAST(SUBSTRING_INDEX(SUBSTRING_INDEX(x.name, ',', yi + 1), ',', -1) AS UNSIGNED) NAME FROM table_name x, (SELECT 0 i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9) y ORDER BY, ID, NAME
