如何执行数据表JOIN操作？求助修正查询指定列的报错SQL语句

Let's walk through why your current SQL might not be running, and get you a working version tailored to your needs:

• Missing required column & extraneous field: You mentioned needing the size column, but your query doesn't include it from the post table. Also, you're selecting p.postId which isn't in your list of desired columns—you can remove that unless you actually need it.
• Verify table/field name correctness: Double-check that your database has tables named tbl_users and post, and that all fields you're referencing exist exactly as written. For example:
  • Ensure tbl_users has userId, firstName, lastName
  • Ensure post has userId, path, file, type, content, size
    Note: Some databases (like MySQL on Linux) are case-sensitive with table/field names, so match the casing exactly as your schema uses.
• Check your WHERE clause value: The userId value 'er.sharmauttam@gmail.com5a51e9ed426f8' looks like an email appended with a string. If userId isn't meant to be an email (maybe you intended to filter by email instead?), adjust the WHERE clause to target the correct field. For example, if tbl_users has an email column, use t.email = 'er.sharmauttam@gmail.com' instead.

Corrected Query (matching your desired columns) #

SELECT 
    t.userId, 
    t.firstName, 
    t.lastName, 
    p.path, 
    p.file, 
    p.type, 
    p.content, 
    p.size
FROM tbl_users t
JOIN post p ON p.userId = t.userId
WHERE t.userId = 'er.sharmauttam@gmail.com5a51e9ed426f8';

If you meant to filter by email instead: #

SELECT 
    t.userId, 
    t.firstName, 
    t.lastName, 
    p.path, 
    p.file, 
    p.type, 
    p.content, 
    p.size
FROM tbl_users t
JOIN post p ON p.userId = t.userId
WHERE t.email = 'er.sharmauttam@gmail.com';

Additional note: If you're expecting results but getting none, it might be because the userId you're filtering on has no corresponding records in the post table. If you want to retrieve the user even if they have no posts, switch to LEFT JOIN instead of JOIN.

内容的提问来源于stack exchange，提问作者uttam sharma