SQL 在 postgres 中解码等价物
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Decode equivalent in postgres
提问by vmb
There is no equivalent to the Oracle's DECODE()'Function InPostgres`. Is there anyone who wrote decode as a Function?
没有等效于Oracle' DECODE()'Function InPostgres`。有没有人把解码写成一个函数？
采纳答案by Mitch Wheat
There is an equivalent. It's called a CASEstatement.
有一个等价物。这叫做CASE声明。
There are two forms of CASE:
CASE有两种形式：
Simple CASE:
简单案例：
CASE search-expression
WHEN expression [, expression [ ... ]] THEN
statements
[ WHEN expression [, expression [ ... ]] THEN
statements
... ]
[ ELSE
statements ]
END CASE;
Searched CASE:
搜索案例：
CASE
WHEN boolean-expression THEN
statements
[ WHEN boolean-expression THEN
statements
... ]
[ ELSE
statements ]
END CASE;
CASEstatements are easier to read; I prefer these over decode()in Oracle.
CASE陈述更容易阅读；decode()在 Oracle 中，我更喜欢这些。
回答by mvp
If you are used to Oracle specific functions, you might want to install PostgreSQL extension orafce.
如果您习惯使用 Oracle 特定功能，则可能需要安装 PostgreSQL 扩展orafce。
Among other Oracle specific functions, orafcealso implements DECODE- one that you are looking for.
在其他 Oracle 特定功能中，orafce还实现DECODE了您正在寻找的功能。
If you are running on Ubuntu, you will simply need to install package postgresql-9.1-orafceto make orafceavailable in your PostgreSQL server.
如果您在 Ubuntu 上运行，您只需要安装软件包postgresql-9.1-orafce即可orafce在您的 PostgreSQL 服务器中使用。
回答by Fernando Meneses Gomes
You can combine NULLIF with COALESCE:
您可以将 NULLIF 与 COALESCE 结合使用：
SELECT COALESCE(NULLIF(value, 0), newValue) FROM table;
SELECT COALESCE(NULLIF(value, 0), newValue) FROM table;
Font: Coalesce for zero instead of null
字体：合并为零而不是空
