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建站问答 时间:2024-11-30 19:24:46
作者:文/会员上传
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在MySQL中,可以使用以下方法将行转列:使用CASE语句:使用多个CASE语句将多行数据转换为单行。每个CASE语句对应一个列,并根据条件将数据填充到对应的列中。例如:SELECT id,MAX(CAS
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在MySQL中,可以使用以下方法将行转列:
SELECT id,MAX(CASE WHEN type = 'A' THEN value END) AS value_a,MAX(CASE WHEN type = 'B' THEN value END) AS value_b,MAX(CASE WHEN type = 'C' THEN value END) AS value_cFROM table_nameGROUP BY id;
SELECT t1.id,t2.value AS value_a,t3.value AS value_b,t4.value AS value_cFROM table_name t1JOIN table_name t2 ON t1.id = t2.id AND t2.type = 'A'JOIN table_name t3 ON t1.id = t3.id AND t3.type = 'B'JOIN table_name t4 ON t1.id = t4.id AND t4.type = 'C';
SELECT id,SUBSTRING_INDEX(GROUP_CONCAT(CASE WHEN type = 'A' THEN value END), ',', 1) AS value_a,SUBSTRING_INDEX(GROUP_CONCAT(CASE WHEN type = 'B' THEN value END), ',', 1) AS value_b,SUBSTRING_INDEX(GROUP_CONCAT(CASE WHEN type = 'C' THEN value END), ',', 1) AS value_cFROM table_nameGROUP BY id;
这些方法可以根据具体的需求选择适合的方式来将行转列。
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