Question

我对PL / SQL很陌生。我在SELECT查询中使用以下嵌套的CASE语句。这遵循WHERE子句。但是，由于此嵌套，查询大约需要6分钟才能完成。如果删除了至少一个CASE块，则查询只需大约1分钟即可完成。有什么方法可以优化此查询？

(case
 when a = 'STAGE PAYMENT' then
 'Y'
 when b not IN ('To be Received', 'Received') then
 'N'
 when c != (d - NVL(e, 0) - NVL(f, 0) - NVL(g, 0)) then
 'Y'
 when NVL(h, 0) + NVL(i, 0) + NVL(j, 0) <> 0 then
    case 
    when c != k then
    'Y'
    when (-l != NVL(e, 0) + NVL(f, 0) + NVL(g, 0) + NVL(m, 0)) then
    'Y' 
    else 'N'
    end 
 else 'N'
 end = 'Y')

我尝试使用IF-ELSE块，但效果不佳。

Answer 1

如何用AND将父案例中的嵌套案例汇总在一起？

(case
 when a = 'STAGE PAYMENT' then
 'Y'
 when b not IN ('To be Received', 'Received') then
 'N'
 when c != (d - NVL(e, 0) - NVL(f, 0) - NVL(g, 0)) then
 'Y'
 when NVL(h, 0) + NVL(i, 0) + NVL(j, 0) <> 0 and c != k then
 'Y'
 when NVL(h, 0) + NVL(i, 0) + NVL(j, 0) <> 0 and (-l != NVL(e, 0) + NVL(f, 0) + NVL(g, 0) + NVL(m, 0)) then
 'Y'
 -- this serves as else 'N' in your code  
 when NVL(h, 0) + NVL(i, 0) + NVL(j, 0) <> 0 then
 'N'
 else 'N'
 end = 'Y')

如何在PL / SQL中优化嵌套的CASE语句

1 个答案: