Question

我在Sybase中有两个表表1

ID   NAME   PRICE
123  KING   12.23
234  KONG   23.43

Table2  
ID  IND  CD
123 1    A

 When we do    "Desc Table2"

Column Name    Data Type   Null   Default Value
ID             Int         N          
IND            BIT         N           0
CD             CHAR        Y

因此，当我连接两个表时，table2有一个永远不能为null的列，默认值为0.

select t1.*, t2.IND, t2.CD
from Table1 t1, Table2 t2
where  t1.ID *= t2.ID

输出：

ID   NAME   PRICE  IND  CD
123  KING   12.23  1    A
234  KONG   23.43  0

期望的输出我想为table2中找不到的字段显示空值。当我尝试更新以使其为null时，它给我的消息NULL不允许。看起来Table2.IND字段最初设置为不允许为空。

输出：

ID   NAME   PRICE  IND  CD
123  KING   12.23  1    A
234  KONG   23.43

如何在我的查询中更改此内容，如果table2中不存在数据，我可以看到NULL。

Answer 1

您应该使用AcceptableIdentifiers : {} AddProxyAuthorizationRules : exists([Type == "http://schemas.microsoft.com/ws/2008/06/identity/claims/groupsid", Value == "S-1-5-32-544", Issuer =~ "^AD AUTHORITY$"]) => issue(Type = "http://schemas.microsoft.com/authorization/claims/permit", Value = "true"); c:[Type == "http://schemas.microsoft.com/ws/2008/06/identity/claims/primarysid", Issuer =~ "^AD AUTHORITY$" ] => issue(store="_ProxyCredentialStore",types=("http ://schemas.microsoft.com/authorization/claims/permit"),query="isProxyTrust ManagerSid({0})", param=c.Value ); c:[Type == "http://schemas.microsoft.com/ws/2008/06/identity/claims/proxytrustid", Issuer =~ "^SELF AUTHORITY$" ] => issue(store="_ProxyCredentialStore",types=("http ://schemas.microsoft.com/authorization/claims/permit"),query="isProxyTrust Provisioned({0})", param=c.Value ); ArtifactDbConnection : Data Source=np:\\.\pipe\microsoft##wid\tsql\query;Initial Catalog=AdfsArtifactStore;Integrated Security=True AuthenticationContextOrder : {urn:oasis:names:tc:SAML:2.0:ac:classes:Password, urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport, urn:oasis:names:tc:SAML:2.0:ac:classes:TLSClient, urn:oasis:names:tc:SAML:2.0:ac:classes:X509...} AutoCertificateRollover : True CertificateCriticalThreshold : 2 CertificateDuration : 365 CertificateGenerationThreshold : 20 CertificatePromotionThreshold : 5 CertificateRolloverInterval : 720 CertificateSharingContainer : CN=6b987b00-35ce-44d9-97c8-561b6f1ac3dd,CN=ADFS,CN=Microsoft,CN=Program Data,DC=sciemetricdev,DC=com CertificateThresholdMultiplier : 1440 ClientCertRevocationCheck : None ContactPerson : DisplayName : ADFS IntranetUseLocalClaimsProvider : False ExtendedProtectionTokenCheck : Allow FederationPassiveAddress : /adfs/ls/ HostName : *************.com HttpPort : 80 HttpsPort : 443 TlsClientPort : 49443 Identifier : http://*******.com/adfs/services/trust InstalledLanguage : en-US LogLevel : {Errors, Information, Verbose, Warnings} MonitoringInterval : 1440 NetTcpPort : 1501 NtlmOnlySupportedClientAtProxy : False OrganizationInfo : PreventTokenReplays : False ProxyTrustTokenLifetime : 21600 ReplayCacheExpirationInterval : 60 SignedSamlRequestsRequired : False SamlMessageDeliveryWindow : 5 SignSamlAuthnRequests : False SsoLifetime : 480 PersistentSsoLifetimeMins : 10080 KmsiLifetimeMins : 1440 PersistentSsoEnabled : True PersistentSsoCutoffTime : 1/1/0001 12:00:00 AM KmsiEnabled : False LoopDetectionEnabled : True LoopDetectionTimeIntervalInSeconds : 20 LoopDetectionMaximumTokensIssuedInInterval : 5 PasswordValidationDelayInMinutes : 60 SendClientRequestIdAsQueryStringParameter : False WIASupportedUserAgents : {MSAuthHost/1.0/In-Domain, MSIE 6.0, MSIE 7.0, MSIE 8.0...} ExtranetLockoutThreshold : 2147483647 ExtranetLockoutEnabled : False ExtranetObservationWindow : 00:30:00：

LEFT JOIN

的 SqlFiddleDemo

输出：

SELECT t1.ID, t1.NAME, t1.PRICE, t2.IND, t2.CD FROM Table1 t1 LEFT JOIN Table2 t2 ON t1.ID = t2.ID;

Answer 2

您在查询结果中看到的是LEFT JOIN（或20岁语法*=）的工作原理。

如果t1中有一行ID而t2并列ID，那么

t1 LEFT JOIN t2 ON t1.ID=t2.ID

会从t1列的NULL和t2值返回此行，因为t2中没有相应的值。

Sybase是否有CASE声明？最有可能的是。您可以使用它将这些NULL值替换为0或任何您需要的值。

select 
    t1.*
    ,CASE WHEN t2.IND IS NULL THEN 0 ELSE t2.IND END AS IND
    ,t2.CD
from Table1 t1, Table2 t2
where  t1.ID *= t2.ID

在T_SQL Null不允许

2 个答案: