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我已經使用netbeans中的GUI將我的組合框與MySQL數據庫綁定在一起。我整年都在組合框中。但是我無法獲得組合框中獨特的年份。在Java中從MySQL中獲取不同的行
The query that displays all year is :
query = "SELECT p FROM Production p WHERE p.yearOfProduction = :yearOfProduction";
我修改了查詢，如下所示，以顯示不同的yearOfProduction。但是查詢不會更改組合框中的列表。
query = "SELECT DISTINCT p FROM Production p WHERE p.yearOfProduction = :yearOfProduction ORDER BY yearOfProduction";
我該怎麼辦？這種類型的查詢對我來說是新的。
的自動生成的Java代碼是：
/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package my_ui;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.persistence.Transient;
/**
*
* @author enjal
*/
@Entity
@Table(name = "production", catalog = "data2", schema = "")
@NamedQueries({
@NamedQuery(name = "Production.findAll", query = "SELECT p FROM Production p"),
@NamedQuery(name = "Production.findByProductionId", query = "SELECT p FROM Production p WHERE p.productionId = :productionId"),
@NamedQuery(name = "Production.findByCropId", query = "SELECT p FROM Production p WHERE p.cropId = :cropId"),
@NamedQuery(name = "Production.findByLocationId", query = "SELECT p FROM Production p WHERE p.locationId = :locationId"),
@NamedQuery(name = "Production.findByArea", query = "SELECT p FROM Production p WHERE p.area = :area"),
@NamedQuery(name = "Production.findByProductionAmount", query = "SELECT p FROM Production p WHERE p.productionAmount = :productionAmount"),
@NamedQuery(name = "Production.findByYieldAmount", query = "SELECT p FROM Production p WHERE p.yieldAmount = :yieldAmount"),
@NamedQuery(name = "Production.findByYearOfProduction", query = "SELECT p FROM Production p WHERE p.yearOfProduction = :yearOfProduction")})
//SELECT DISTINCT year_of_production FROM `production` ORDER BY year_of_production ASC
public class Production implements Serializable {
@Transient
private PropertyChangeSupport changeSupport = new PropertyChangeSupport(this);
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Basic(optional = false)
@Column(name = "production_id")
private Integer productionId;
@Basic(optional = false)
@Column(name = "crop_id")
private int cropId;
@Basic(optional = false)
@Column(name = "location_id")
private String locationId;
@Basic(optional = false)
@Column(name = "area")
private double area;
@Basic(optional = false)
@Column(name = "production_amount")
private String productionAmount;
@Basic(optional = false)
@Column(name = "yield_amount")
private double yieldAmount;
@Basic(optional = false)
@Column(name = "year_of_production")
private String yearOfProduction;
public Production() {
}
public Production(Integer productionId) {
this.productionId = productionId;
}
public Production(Integer productionId, int cropId, String locationId, double area, String productionAmount, double yieldAmount, String yearOfProduction) {
this.productionId = productionId;
this.cropId = cropId;
this.locationId = locationId;
this.area = area;
this.productionAmount = productionAmount;
this.yieldAmount = yieldAmount;
this.yearOfProduction = yearOfProduction;
}
public Integer getProductionId() {
return productionId;
}
public void setProductionId(Integer productionId) {
Integer oldProductionId = this.productionId;
this.productionId = productionId;
changeSupport.firePropertyChange("productionId", oldProductionId, productionId);
}
public int getCropId() {
return cropId;
}
public void setCropId(int cropId) {
int oldCropId = this.cropId;
this.cropId = cropId;
changeSupport.firePropertyChange("cropId", oldCropId, cropId);
}
public String getLocationId() {
return locationId;
}
public void setLocationId(String locationId) {
String oldLocationId = this.locationId;
this.locationId = locationId;
changeSupport.firePropertyChange("locationId", oldLocationId, locationId);
}
public double getArea() {
return area;
}
public void setArea(double area) {
double oldArea = this.area;
this.area = area;
changeSupport.firePropertyChange("area", oldArea, area);
}
public String getProductionAmount() {
return productionAmount;
}
public void setProductionAmount(String productionAmount) {
String oldProductionAmount = this.productionAmount;
this.productionAmount = productionAmount;
changeSupport.firePropertyChange("productionAmount", oldProductionAmount, productionAmount);
}
public double getYieldAmount() {
return yieldAmount;
}
public void setYieldAmount(double yieldAmount) {
double oldYieldAmount = this.yieldAmount;
this.yieldAmount = yieldAmount;
changeSupport.firePropertyChange("yieldAmount", oldYieldAmount, yieldAmount);
}
public String getYearOfProduction() {
return yearOfProduction;
}
public void setYearOfProduction(String yearOfProduction) {
String oldYearOfProduction = this.yearOfProduction;
this.yearOfProduction = yearOfProduction;
changeSupport.firePropertyChange("yearOfProduction", oldYearOfProduction, yearOfProduction);
}
@Override
public int hashCode() {
int hash = 0;
hash += (productionId != null ? productionId.hashCode() : 0);
return hash;
}
@Override
public boolean equals(Object object) {
// TODO: Warning - this method won't work in the case the id fields are not set
if (!(object instanceof Production)) {
return false;
}
Production other = (Production) object;
if ((this.productionId == null && other.productionId != null) || (this.productionId != null && !this.productionId.equals(other.productionId))) {
return false;
}
return true;
}
@Override
public String toString() {
return "" + yearOfProduction + "";
}
public void addPropertyChangeListener(PropertyChangeListener listener) {
changeSupport.addPropertyChangeListener(listener);
}
public void removePropertyChangeListener(PropertyChangeListener listener) {
changeSupport.removePropertyChangeListener(listener);
}
}
您所查詢的是尋找不同的生產實例，而不是不同的生產年份。 – JamesB
JamesB我是這種類型的查詢的新手..你可以寫我單行代碼來做到這一點......這將是非常有幫助的 – enjal