如果列存在于 PostgreSQL 9+ 中，如何删除它？

How to drop column if it exists in PostgreSQL 9+?

提问by user3521432

I am trying to drop a column from a table. How can I check if the column exists or not?

我正在尝试从表中删除一列。如何检查该列是否存在？

I went through the documentation at https://www.postgresql.org/docs/9.2/static/sql-altertable.html, but didn't find any example how to do it.

我浏览了https://www.postgresql.org/docs/9.2/static/sql-altertable.html 上的文档，但没有找到任何示例。

Even found How to check if a column exists in a SQL Server table?, but it does not seem relevant.

甚至发现如何检查 SQL Server 表中是否存在列？，但似乎并不相关。

回答by user3521432

You just need to add IF EXISTto your DROP COLUMNstatement:

你只需要IF EXIST在你的DROP COLUMN声明中添加：

ALTER TABLE tableName
DROP COLUMN IF EXISTS columnName;

回答by Piyush Sharma

You can also try via IF EXISTS Method which work great while we are using migration

您也可以尝试通过 IF EXISTS 方法，该方法在我们使用迁移时效果很好

DO $$

BEGIN

    IF EXISTS(
    SELECT column_name FROM information_schema.columns WHERE table_name = tableName AND column_name = columnName)
    THEN
        ALTER TABLE tableName DROP COLUMN columnName;
    END IF;

END $$;