sql - 如何在 postgres 9.5 中正确执行 upsert

Question

upsert 与 postgresql 9.5 的正确语法，下面的查询显示 column reference "gallery_id"is ambiguous 错误，为什么？

var dbQuery = `INSERT INTO category_gallery (
  category_id, gallery_id, create_date, create_by_user_id
  ) VALUES ($1, $2, $3, $4)
  ON CONFLICT (category_id)
  DO UPDATE SET
  category_id = $1,
  last_modified_date = $3,
  last_modified_by_user_id = $4
  WHERE gallery_id = $2`;

我尝试将 WHERE gallery_id = $2; 更改为 WHERE category_gallery.gallery_id = $2; 然后显示错误 没有与 ON CONFLICT 匹配的唯一或排除约束specification，但我不想将 gallery_id 或 category_id 设置为唯一，因为我想确保两列相同，然后进行更新....

如何在 postgres 9.5 中正确执行 upsert？

如果 ON CONFLICT 需要唯一列，我应该使用其他方法吗？如何？

我想确定多个列都冲突然后做更新，什么是正确的用法

var dbQuery = `INSERT INTO category_gallery (
  category_id, gallery_id, create_date, create_by_user_id
  ) VALUES ($1, $2, $3, $4)
  ON CONFLICT (category_id, gallery_id)
  DO UPDATE SET
  category_id = $1,
  last_modified_date = $3,
  last_modified_by_user_id = $4
  WHERE gallery_id = $2`;


var dbQuery = `INSERT INTO category_gallery (
  category_id, gallery_id, create_date, create_by_user_id
  ) VALUES ($1, $2, $3, $4)
  ON CONFLICT (category_id AND gallery_id)
  DO UPDATE SET
  category_id = $1,
  last_modified_date = $3,
  last_modified_by_user_id = $4
  WHERE gallery_id = $2`;

表(category_id，gallery_id 不是唯一的列)

category_id | gallery_id | create_date | create_by_user_id | last_modified_date | last_modified_by_user_id
1 | 1 | ...  
1 | 2 | ...
2 | 2 | ...
1 | 3 | ...

Answer 1

ON CONFLICT 结构需要一个UNIQUE 约束才能工作。来自 INSERT .. ON CONFLICT clause 上的文档:

The optional ON CONFLICT clause specifies an alternative action to raising a unique violation or exclusion constraint violation error. For each individual row proposed for insertion, either the insertion proceeds, or, if an arbiter constraint or index specified by conflict_target is violated, the alternative conflict_action is taken. ON CONFLICT DO NOTHING simply avoids inserting a row as its alternative action. ON CONFLICT DO UPDATE updates the existing row that conflicts with the row proposed for insertion as its alternative action.

现在，问题不是很清楚，但您可能需要对 2 列组合的 UNIQUE 约束:(category_id, gallery_id)。

ALTER TABLE category_gallery
    ADD CONSTRAINT category_gallery_uq
    UNIQUE (category_id, gallery_id) ;

如果要插入的行与表中已有行的两个值匹配，则执行UPDATE，而不是INSERT:

INSERT INTO category_gallery (
  category_id, gallery_id, create_date, create_by_user_id
  ) VALUES ($1, $2, $3, $4)
  ON CONFLICT (category_id, gallery_id)
  DO UPDATE SET
    last_modified_date = EXCLUDED.create_date,
    last_modified_by_user_id = EXCLUDED.create_by_user_id ;

您可以使用 UNIQUE 约束的任一列:

  ON CONFLICT (category_id, gallery_id) 

或约束名称:

  ON CONFLICT ON CONSTRAINT category_gallery_uq