[英]SQL query with poor join performance
我在为Oracle 12c编写的查询中遇到了非常糟糕的性能。 这可能与我对连接的低效使用有关,并希望有人可以帮我解决我出错的地方。 我的查询目前正在运行一分钟 。
我正在尝试返回表和列名称:
目前我的查询如下
SELECT consCols.table_name, consCols.column_name
FROM all_cons_columns consCols
INNER JOIN all_constraints cons
ON cons.constraint_name = consCols.constraint_name
INNER JOIN all_tab_columns cols
ON consCols.table_name = cols.table_name AND consCols.column_name = cols.column_name
WHERE cons.constraint_type = 'P'
AND cons.owner = 'MY_OWNER'
AND cols.data_type = 'NUMBER'
AND consCols.table_name IN(
SELECT consCols2.table_name
FROM all_cons_columns consCols2
INNER JOIN all_constraints cons2
ON cons2.constraint_name = consCols2.constraint_name
WHERE cons2.constraint_type = 'P'
AND cons2.owner = 'MY_OWNER'
GROUP BY consCols2.table_name
HAVING COUNT(consCols2.table_name) = 1
);
谢谢你能给我的任何帮助。
使用分析函数会加快查询速度吗?
SELECT table_name, column_name
FROM (SELECT consCols.table_name, consCols.column_name, cols.data_type,
COUNT(*) OVER (PARTITION BY consCols.table_name) as cnt
FROM all_cons_columns consCols INNER JOIN
all_constraints cons
ON cons.constraint_name = consCols.constraint_name INNER JOIN
all_tab_columns cols
ON consCols.table_name = cols.table_name AND consCols.column_name = cols.column_name
WHERE cons.constraint_type = 'P' AND
cons.owner = 'MY_OWNER'
) tc
WHERE data_type = 'NUMBER' AND cnt = 1;
甚至聚合?
SELECT consCols.table_name, consCols.column_name
FROM all_cons_columns consCols INNER JOIN
all_constraints cons
ON cons.constraint_name = consCols.constraint_name INNER JOIN
all_tab_columns cols
ON consCols.table_name = cols.table_name AND consCols.column_name = cols.column_name
WHERE cons.constraint_type = 'P' AND
cons.owner = 'MY_OWNER'
GROUP BY consCols.table_name, consCols.column_name
HAVING COUNT(*) = 1 AND
MAX(cols.data_type) = 'NUMBER';
这是第三种选择:
SELECT consCols.table_name, consCols.column_name
FROM all_cons_columns consCols INNER JOIN
all_constraints cons
ON cons.constraint_name = consCols.constraint_name INNER JOIN
all_tab_columns cols
ON consCols.table_name = cols.table_name AND consCols.column_name = cols.column_name
WHERE cons.constraint_type = 'P' AND
cons.owner = 'MY_OWNER' AND
cols.data_type = 'NUMBER' AND
NOT EXISTS (SELECT 1
FROM all_cons_columns acc
WHERE acc.constraint_name = consCols.constraint_name AND
acc.table_name = consCols.table_name AND
acc.column_name <> consCols.column_name
);
这消除了聚合,查找应该相对较快。
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