寫 sql 唔同你寫 program 唔係入個阿媽某個 column 既 value 再隊入去 另一個 table 當 parameter

係乜都用左大 join 先 唔o岩用 ? 日期大過 effective date 既 cost ? join 左先啦

最後先 filter

唔理架 乜都 join 十幾萬 record 大溶爐先 最後想要咩 record 先慢慢 filter

A1 單要配 某個日子既 cost ?

A1(which is Date3)-Cost1 Date1 A1(which is Date3)-Cost2 Date2 A1(which is Date3)-Cost3 Date3

join 晒先 再啄走唔要個d 留翻一個 係我夠知 A1 – Date3 先o岩 你 join 左再用 on 去啄 如果唔係有乜法 je~