select nvl(trunc(null),trunc(sysdate)) from dual;
执行上述查询时，我收到以下错误
ORA-00932: inconsistent datatypes: expected NUMBER got DATE
看起来当我接受字符串或数字而不是trunc(sysdate)时，它运行正常。
答案 0 :(得分：5)
来自here：
NVL的第一个参数是确定的预期数据类型 返回列，截断函数默认为NUMBER 因为它的参数是NULL。 NVL的第二个参数需要 匹配它没有的数据类型，因为它是一个日期。
SQL> select nvl(trunc(sysdate), sysdate) as mydate from dual;
MYDATE
-------------------
26/05/2006 00:00:00
SQL> select nvl(trunc(null), sysdate) as mydate from dual;
select nvl(trunc(null), sysdate) as mydate from dual
*
ERROR at line 1:
ORA-00932: inconsistent datatypes: expected NUMBER got DATE
或者你可以这样做：
SELECT NVL(TO_DATE(TRUNC(NULL)),SYSDATE) FROM dual;
答案 1 :(得分：1)
第二个参数必须与第一个参数具有相同的数据类型。 package Assignment_1;
//Begin Class Definition
public class AddressBook {
// Member variables
private String businessPhone;
private String cellPhone;
private String facebookId;
private String firstName;
private String homeAddress;
private String homePhone;
private String lastName;
private String middleName;
private String personalWebSite;
private String skypeId;
//Constructors
public AddressBook (String firstName, String middleName, String lastName, String homeAddress, String businessPhone, String homePhone, String cellPhone, String skypeId, String facebookId, String personalWebSite) {
this.firstName = firstName;
this.middleName = middleName;
this.lastName = lastName;
this.homeAddress = homeAddress;
this.businessPhone = businessPhone;
this.homePhone = homePhone;
this.cellPhone = cellPhone;
this.skypeId = skypeId;
this.facebookId = facebookId;
this.personalWebSite = personalWebSite;
}
public AddressBook (String firstName) {
this.firstName = firstName;
}
public AddressBook(String firstName, String middleName) {
this.firstName = firstName;
this.middleName = middleName;
}
public AddressBook (String firstName, String middleName, String lastName) {
this.firstName = firstName;
this.middleName = middleName;
this.lastName = lastName;
}
// Getters and setters
public String getFirstName() {
return firstName;
}
public String getMiddleName() {
return middleName;
}
public String getLastName() {
return lastName;
}
public String getHomeAddress() {
return homeAddress;
}
public String getBusinessPhone() {
return businessPhone;
}
public String getHomePhone() {
return homePhone;
}
public String getCellPhone() {
return cellPhone;
}
public String getSkypeId() {
return skypeId;
}
public String getFacebookId() {
return facebookId;
}
public String getPersonalWebsite() {
return personalWebSite;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public void setMiddleName(String middleName) {
this.middleName = middleName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public void setHomeAddress(String homeAddress) {
this.homeAddress = homeAddress;
}
public void setBusinessPhone(String businessPhone) {
this.businessPhone = businessPhone;
}
public void setHomePhone(String homePhone) {
this.homePhone = homePhone;
}
public void setCellPhone(String cellPhone) {
this.cellPhone = cellPhone;
}
public void setSkypeId(String skypeId) {
this.skypeId = skypeId;
}
public void setFacebookId(String facebookId) {
this.facebookId = facebookId;
}
public void setPersonalWebSite(String personalWebSite) {
this.personalWebSite = personalWebSite;
}
// Public methods
public static void compareNames(String name1, String name2) {
if(name1.equals(name2)) {
System.out.println(name1);
System.out.println(name2);
System.out.println("The names are the same.");
} else {
System.out.println(name1);
System.out.println(name2);
System.out.println("The names appear to be different.");
}
}
************************************************************
package Assignment_1;
public class BanffMarathonRunner extends AddressBook {
// Member variables
private int time;
private int years;
// Constructors
public BanffMarathonRunner(String firstName, String lastName, int min, int yr) {
super(firstName, lastName);
time = min;
years = yr;
}
// Getters and Setters
public int getTime() {
return time;
}
public void setTime(int time) {
this.time = time;
}
public int getYears() {
return years;
}
public void setYears(int years) {
this.years = years;
}
}
************************************************************
package Assignment_1;
import Assignment_1.BanffMarathonRunner;
public class TestBanffMarathonRunner {
public static void main(String[] args) {
BanffMarathonRunner r1 = new BanffMarathonRunner("Elena", "Brandon", 341, 1);
System.out.print(r1.getLastName());
}
}
}函数已重载。显然，当你传递trunc时，它会将值解释为数字并返回一个数字。以下任何一项工作：
null跟进：
如果正在使用的变量被正确定义为日期，那么您应该没有问题。例如，以下运行没有错误：
SELECT NVL (NULL, TRUNC (SYSDATE)) FROM DUAL;
SELECT NVL (TRUNC (TO_DATE (NULL)), TRUNC (SYSDATE)) FROM DUAL;
SELECT NVL (TRUNC (CAST (NULL AS DATE)), TRUNC (SYSDATE)) FROM DUAL;
为了得到实际解决问题的答案，我建议编辑问题以包含实际证明问题的代码。