postgresql 如何比较postgres中的两个表
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/4814597/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to compare two tables in postgres
提问by jnivasreddy
I want compare two column values which come from two different queries. Can anyone suggest a query which compares two columns in Postgres?
我想比较来自两个不同查询的两个列值。谁能建议一个比较 Postgres 中两列的查询？
回答by Mike Sherrill 'Cat Recall'
Well, the easiest to understand--but not necessarily the fastest--is probably something like this. (But you might mean something else by "compare".)
嗯，最容易理解——但不一定是最快的——可能是这样的。（但“比较”可能是其他意思。）
-- Values in column1 that aren't in column2.
SELECT column1 FROM query1
WHERE column1 NOT IN (SELECT column2 FROM query2);
-- Values in column2 that aren't in column1.
SELECT column2 FROM query2
WHERE column2 NOT IN (SELECT column1 FROM query1);
-- Values common to both column1 and column2
SELECT q1.column1 FROM query1 q1
INNER JOIN query2 q2 ON (q1.column1 = q2.column2);
You can also do this in a single statement to give you a visual comparison. A FULL OUTER JOINreturns all the values in both columns, with matching values in the same row, and NULLwhere one column is missing a value that's in the other column.
您也可以在单个语句中执行此操作，以便进行视觉比较。AFULL OUTER JOIN返回两列中的所有值，在同一行中具有匹配值，并且NULL其中一列缺少另一列中的值。
SELECT q1.column1, q2.column2 FROM query1 q1
FULL OUTER JOIN query2 q2 ON (q1.column1 = q2.column2);
