我正在我的 JAVA 应用程序和 PostgreSQL 数据库中进行过滤搜索。
我有以下 PostgreSQL 查询来选择有关航类的数据:
String query = "SELECT flight.flight_id, route.from_location, route.to_location, flight.base_cost, flight.departure_date, flight.departure_time, flight.arrival_date, flight.arrival_time, aircraft.manufacturer, aircraft.seats " +
"FROM flight " +
"INNER JOIN route ON flight.route_id = route.route_id " +
"INNER JOIN aircraft ON flight.aircraft_id = aircraft.aircraft_id " +
"WHERE " +
"(from_location = CASE WHEN ? IS NULL THEN from_location ELSE ? END) AND " +
"(to_location = CASE WHEN ? IS NULL THEN to_location ELSE ? END) AND " +
"(base_cost = CASE WHEN ? IS NULL THEN base_cost ELSE ? END) AND " +
"(departure_date = CASE WHEN ? IS NULL THEN departure_date ELSE ? END) AND " +
"(departure_time = CASE WHEN ? IS NULL THEN departure_time ELSE ? END) AND " +
"(arrival_date = CASE WHEN ? IS NULL THEN arrival_date ELSE ? END) AND " +
"(arrival_time = CASE WHEN ? IS NULL THEN arrival_time ELSE ? END)";
然后我有一个像这样的Java代码:
ResultSet rs = null;
PreparedStatement prepStatement = connection.prepareStatement(query);
try {
if (!showFromTxtField.getText().trim().isEmpty()) {
prepStatement.setString(1, showFromTxtField.getText());
prepStatement.setString(2, showFromTxtField.getText());
} else {
prepStatement.setNull(1, java.sql.Types.VARCHAR );
prepStatement.setNull(2, java.sql.Types.VARCHAR );
}
if (!showToTxtField.getText().trim().isEmpty()) {
prepStatement.setString(3, showToTxtField.getText());
prepStatement.setString(4, showToTxtField.getText());
} else {
prepStatement.setNull(3, java.sql.Types.VARCHAR );
prepStatement.setNull(4, java.sql.Types.VARCHAR );
}
if (!showCostTxtField.getText().trim().isEmpty()) {
prepStatement.setFloat(5, Float.parseFloat(showCostTxtField.getText()));
prepStatement.setFloat(6, Float.parseFloat(showCostTxtField.getText()));
} else {
prepStatement.setNull(5, java.sql.Types.FLOAT );
prepStatement.setNull(6, java.sql.Types.FLOAT);
}
LocalDate depDate = showDepDateDatePicker.getValue();
if (depDate != null) {
prepStatement.setDate(7, Date.valueOf(depDate));
prepStatement.setDate(8, Date.valueOf(depDate));
} else {
prepStatement.setNull(7, java.sql.Types.DATE );
prepStatement.setNull(8, java.sql.Types.DATE);
}
if (!showDepTimeTxtField.getText().trim().isEmpty()) {
DateFormat formatter = new SimpleDateFormat("HH:mm:ss");
try {
Time timeValue = new Time(formatter.parse(showDepTimeTxtField.getText()).getTime());
prepStatement.setTime(9, timeValue);
prepStatement.setTime(10, timeValue);
} catch (ParseException e) {
e.printStackTrace();
}
} else {
prepStatement.setNull(9, java.sql.Types.TIME );
prepStatement.setNull(10, java.sql.Types.TIME );
}
LocalDate arrDate = showArrDatePicker.getValue();
if (arrDate != null) {
prepStatement.setDate(11, Date.valueOf(arrDate));
prepStatement.setDate(12, Date.valueOf(arrDate));
} else {
prepStatement.setNull(11, java.sql.Types.DATE );
prepStatement.setNull(12, java.sql.Types.DATE);
}
if (!showArrTimeTxtField.getText().trim().isEmpty()) {
DateFormat formatter = new SimpleDateFormat("HH:mm:ss");
try {
Time timeValue = new Time(formatter.parse(showArrTimeTxtField.getText()).getTime());
prepStatement.setTime(13, timeValue);
prepStatement.setTime(14, timeValue);
} catch (ParseException e) {
e.printStackTrace();
}
} else {
prepStatement.setNull(13, java.sql.Types.TIME );
prepStatement.setNull(14, java.sql.Types.TIME );
}
rs = prepStatement.executeQuery();
} catch (SQLException e) {
e.printStackTrace();
}
因此,重点是仅返回那些符合文本字段条件的航类。如果任何文本字段留空,则查询应返回符合该特定条件的所有航类,但使用其他非空条件进行过滤。
参数 $9 处有错误。
当我将输入到 showDepTimeTxtField
中的 String
(例如“18:00:00”)转换为 java.sql.Time
对象时,我可以用作 prepStatement
方法 setTime()
的输入参数,我的查询应仅返回 departure_time
与输入时间相同的航类(满足其他条件)进入文本字段。如果文本字段留空且没有 String
输入,则我的查询应从我的数据库中返回具有任何 departure_time
的航类。
我的问题是,当我运行代码时出现以下错误:
org.postgresql.util.PSQLException:错误:无法确定参数 $9 的数据类型,无论我用字符串填充 departureTimeTxtField
还是将其留空,因此参数 departure_time
应设置为 NULL,我的查询应返回包含所有 departure_time
的航类。
所以我假设我的 setTime()
方法参数 timeValue
以及从 String
到 java.sql 的转换有问题。时间
。
如何进行正确的转换以便消除该错误?
编辑:更新了 SQL 查询和 Java 源代码。
最佳答案
我能够通过使用 COALESCE()
而不是 CASE WHEN ...
来解决该问题:
String query = "SELECT * FROM flights WHERE departure_time = COALESCE(?, departure_time)";
关于java - 根据用户输入在PreparedStatement中使用setTime()或setNull(),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/36379212/