Question

我有一个输入屏幕，可以输入8个输入值。输入值如下

tCustomerIDStart  -  tCustomerIDEnd
tProjectIDStart - tProjectIDEnd
tDateStart - tDateEnd
tProjectStatusStart - tProjectStatusEnd

一旦用户点击我的表单上的提交，我想在我的SQLite数据库上执行查询。我在下面的查询是我想要的基本概要，但是如果用户只输入一对搜索条件，我不太确定如何构造查询。 tDateStart - tDateEnd。我可以获取查询以省略其他子句吗？在调用其他子句之前，WHERE语句中的第一个子句是否始终必须求值为true。如果填写了所有字段，我可以构造一个查询，主要是使用WHERE语法然后使用AND来构建子句的情况。但是，sql是否可以忽略一对空的搜索条件字段？

  "SELECT  project.start_date, project.projectID, project.project_title, customer.customer, " &\
  "project.end_date, project.project_manager, project_status.project_status " &\
  "FROM project " &\
  "LEFT JOIN customer " &\
  "ON project.customerID=customer.customerID " &\
  "LEFT JOIN project_status " &\
  "ON project.project_statusID=project_status.project_statusID " &\
  "WHERE project.projectID BETWEEN " & tProjectIDStart & " AND " & tProjectIDEnd & " " &\
  "OR customer.customerID BETWEEN " & tCustomerIDStart & " AND " & tCustomerIDEnd & " " &\
  "OR project.project_status_id BETWEEN " & tStatusIDStart & " AND " & tStatusIDEnd & " " &\
  "OR project.start_date >= " & tDateStart & " AND " & tDateEnd & " " &\
  "ORDER BY date(project.start_date) ASC "

Answer 1

根据这些值是空还是空来构建查询

如果您开始使用1=1之类的内容，那么您只需应用其他过滤器并使用AND启动所有过滤器

sql = "SELECT  project.start_date, project.projectID, project.project_title, customer.customer, " &\
  "project.end_date, project.project_manager, project_status.project_status " &\
  "FROM project " &\
  "LEFT JOIN customer " &\
  "ON project.customerID=customer.customerID " &\
  "LEFT JOIN project_status " &\
  "ON project.project_statusID=project_status.project_statusID " &\
  "WHERE 1=1 "

if (tProjectIDStart != "" And tProjectIDEnd != "")
{
    sql = sql & " AND project.projectID BETWEEN " & tProjectIDStart & " AND " & tProjectIDEnd & " "
}
etc.. 

sql = sql &  "ORDER BY date(project.start_date) ASC "

sql和多个查询

1 个答案: