如何在 SQL 中选择所有值并隐藏 NULL 值? [英] How to select all values and hide NULL values in SQL?

问题描述

所以在我的数据库中，某些行具有 NULL 值，当我从表中选择 * 时，该 NULL 值也显示为文本null".所以我想隐藏所有 NULL 值.有没有人有查询的想法?谢谢！

so in my database some rows have NULL values, and when I select * from table, that NULL values also shows as text "null". So I want to hide all NULL values. Does anyone have idea for query? Thanks!

这是我在数据库中的输入:

this is my input in DB:

db.execSQL("CREATE TABLE IF NOT EXISTS table (name VARCHAR, kg VARCHAR,   pod                 VARCHAR,reps VARCHAR, time VARCHAR );");
  db.execSQL("INSERT INTO table VALUES('name 1',NULL,NULL , NULL , '"+s+"');");
 db.execSQL("INSERT INTO table VALUES(NULL,'S 1','"+ee5+"' , '"+ee+"' , '"+s+"');");
 db.execSQL("INSERT INTO table VALUES(NULL,'S 2','"+ee6+"' , '"+ee2+"', '"+s+"');");
 db.execSQL("INSERT INTO table VALUES(NULL,'S 3','"+ee7+"' , '"+ee3+"', '"+s+"');");
 db.execSQL("INSERT INTO table VALUES(NULL,'S 4','"+ee8+"' , '"+ee4+"', '"+s+"');");

推荐答案

这就是您要找的:

SELECT x, y, etc, CASE WHEN field IS NOT NULL THEN field ELSE '' END AS hehe FROM table;

编辑:添加到您的评论中，一旦您知道如何为一栏做这件事，这将变得非常简单.对所有列应用相同的方法.在 SO 不要期望家庭作业完成，而是期望帮助解决您的问题，最终您自己必须这样做.

Edit: Addin to your comments, this is pretty trivial once you know how to do it for one column. Apply the same for all columns. In SO dont expect homeworks to get done, instead expect a help to solve your problem which ultimately you yourself have to do.

顺便说一句，这是如何..

Btw, here is how..

SELECT COALESCE(name, ''), COALESCE(kg, ''), COALESCE(pod, ''), COALESCE(reps, ''), 
       COALESCE(time, '') 
FROM   table

你在这个贴子里有三个不错的方法(包括我的)，我个人觉得另外两个更直观.通过应用与我展示的相同的逻辑来使用 any.

You have three good methods in this thread (including mine), and I personally feel the other two are more intuitive. Use any by applying the same logic as I have shown.

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