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遞歸查詢是一種在數(shù)據(jù)庫中查詢具有層次結(jié)構(gòu)或嵌套關(guān)系的數(shù)據(jù)的方法。在處理復(fù)雜條件時(shí),可以使用以下方法:
WITH RecursiveCTE AS (
-- 基本查詢
SELECT * FROM your_table WHERE some_condition
UNION ALL
-- 遞歸查詢
SELECT t.* FROM your_table t
JOIN RecursiveCTE rcte ON t.parent_id = rcte.id
WHERE some_complex_condition
)
SELECT * FROM RecursiveCTE;
SELECT id, parent_id,
CASE
WHEN some_condition THEN 'A'
WHEN some_other_condition THEN 'B'
ELSE 'C'
END AS category
FROM your_table
WHERE category IN ('A', 'B');
SELECT * FROM (
SELECT id, parent_id, some_column
FROM your_table
WHERE some_condition
UNION ALL
SELECT t.id, t.parent_id, t.some_column
FROM your_table t
JOIN your_table p ON t.parent_id = p.id
WHERE some_complex_condition
) AS subquery
ORDER BY some_column DESC;
SELECT t1.*, t2.some_column
FROM your_table t1
JOIN another_table t2 ON t1.id = t2.related_id
WHERE some_complex_condition;
SELECT parent_id, COUNT(*) as child_count
FROM your_table
WHERE some_condition
GROUP BY parent_id;
通過使用這些方法,可以在遞歸查詢中處理復(fù)雜條件,從而更好地滿足實(shí)際需求。
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