SQL 查詢構建器
從 CREATE TABLE 模式開始(貼上 DDL 或手動定義列),勾選所需列,新增 WHERE / JOIN / ORDER BY 子句,構建器會在你的方言下生成可執行的 SELECT、INSERT、UPDATE 或 DELETE 骨架。它只是起步腳手架——執行前請務必檢查生成的 SQL。完全本地執行。
所選列的值 (留空 = 佔位符 / NULL)
JOINs, GROUP BY and the WHERE/HAVING split
INNER JOIN keeps only rows that match on both sides; LEFT JOIN keeps every left row and fills the missing right side with NULL. WHERE filters rows before grouping, HAVING filters after aggregation — which is exactly why SUM(...) belongs in HAVING, not WHERE.
With GROUP BY, the SELECT list may only contain grouped columns and aggregates — anything else is the classic “not in GROUP BY” error.