我有这个Oracle SQL请求：
[INFO] Scanning for projects...
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[INFO] ---------------------------< theo.jpa:demo >----------------------------
[INFO] Building example 0.0.1-SNAPSHOT
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[INFO] --- maven-resources-plugin:3.1.0:resources (default-resources) @ demo ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
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[INFO] --- maven-compiler-plugin:3.8.0:compile (default-compile) @ demo ---
[INFO] Nothing to compile - all classes are up to date
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[INFO] --- maven-resources-plugin:3.1.0:testResources (default-testResources) @ demo ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/theodosiostziomakas/Desktop/Java Spring Tutorials/spring-boot-spring-mvc-bootstrap/src/test/resources
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[INFO] --- maven-compiler-plugin:3.8.0:testCompile (default-testCompile) @ demo ---
[INFO] Nothing to compile - all classes are up to date
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[INFO] --- maven-surefire-plugin:2.22.1:test (default-test) @ demo ---
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[INFO] T E S T S
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[INFO] Running theo.jpa.demo.ExampleApplicationTests
17:24:41.733 [main] DEBUG org.springframework.test.context.junit4.SpringJUnit4ClassRunner - SpringJUnit4ClassRunner constructor called with [class theo.jpa.demo.ExampleApplicationTests]
17:24:41.742 [main] DEBUG org.springframework.test.context.BootstrapUtils - Instantiating CacheAwareContextLoaderDelegate from class [org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate]
17:24:41.756 [main] DEBUG org.springframework.test.context.BootstrapUtils - Instantiating BootstrapContext using constructor [public org.springframework.test.context.support.DefaultBootstrapContext(java.lang.Class,org.springframework.test.context.CacheAwareContextLoaderDelegate)]
17:24:41.787 [main] DEBUG org.springframework.test.context.BootstrapUtils - Instantiating TestContextBootstrapper for test class [theo.jpa.demo.ExampleApplicationTests] from class [org.springframework.boot.test.context.SpringBootTestContextBootstrapper]
17:24:41.991 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper - Neither @ContextConfiguration nor @ContextHierarchy found for test class [theo.jpa.demo.ExampleApplicationTests], using SpringBootContextLoader
17:24:42.007 [main] DEBUG org.springframework.test.context.support.AbstractContextLoader - Did not detect default resource location for test class [theo.jpa.demo.ExampleApplicationTests]: class path resource [theo/jpa/demo/ExampleApplicationTests-context.xml] does not exist
17:24:42.011 [main] DEBUG org.springframework.test.context.support.AbstractContextLoader - Did not detect default resource location for test class [theo.jpa.demo.ExampleApplicationTests]: class path resource [theo/jpa/demo/ExampleApplicationTestsContext.groovy] does not exist
17:24:42.011 [main] INFO org.springframework.test.context.support.AbstractContextLoader - Could not detect default resource locations for test class [theo.jpa.demo.ExampleApplicationTests]: no resource found for suffixes {-context.xml, Context.groovy}.
17:24:42.013 [main] INFO org.springframework.test.context.support.AnnotationConfigContextLoaderUtils - Could not detect default configuration classes for test class [theo.jpa.demo.ExampleApplicationTests]: ExampleApplicationTests does not declare any static, non-private, non-final, nested classes annotated with @Configuration.
17:24:42.135 [main] DEBUG org.springframework.test.context.support.ActiveProfilesUtils - Could not find an 'annotation declaring class' for annotation type [org.springframework.test.context.ActiveProfiles] and class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.349 [main] DEBUG org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider - Identified candidate component class: file [/Users/theodosiostziomakas/Desktop/Java Spring Tutorials/spring-boot-spring-mvc-bootstrap/target/classes/theo/jpa/demo/ExampleApplication.class]
17:24:42.351 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper - Found @SpringBootConfiguration theo.jpa.demo.ExampleApplication for test class theo.jpa.demo.ExampleApplicationTests
17:24:42.600 [main] DEBUG org.springframework.boot.test.context.SpringBootTestContextBootstrapper - @TestExecutionListeners is not present for class [theo.jpa.demo.ExampleApplicationTests]: using defaults.
17:24:42.603 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper - Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.boot.test.mock.mockito.MockitoTestExecutionListener, org.springframework.boot.test.mock.mockito.ResetMocksTestExecutionListener, org.springframework.boot.test.autoconfigure.restdocs.RestDocsTestExecutionListener, org.springframework.boot.test.autoconfigure.web.client.MockRestServiceServerResetTestExecutionListener, org.springframework.boot.test.autoconfigure.web.servlet.MockMvcPrintOnlyOnFailureTestExecutionListener, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverTestExecutionListener, org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
17:24:42.742 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper - Using TestExecutionListeners: [org.springframework.test.context.web.ServletTestExecutionListener@692f203f, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@48f2bd5b, org.springframework.boot.test.mock.mockito.MockitoTestExecutionListener@7b2bbc3, org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener@a1153bc, org.springframework.test.context.support.DirtiesContextTestExecutionListener@1aafa419, org.springframework.test.context.transaction.TransactionalTestExecutionListener@47eaca72, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@55141def, org.springframework.boot.test.mock.mockito.ResetMocksTestExecutionListener@55182842, org.springframework.boot.test.autoconfigure.restdocs.RestDocsTestExecutionListener@3270d194, org.springframework.boot.test.autoconfigure.web.client.MockRestServiceServerResetTestExecutionListener@235834f2, org.springframework.boot.test.autoconfigure.web.servlet.MockMvcPrintOnlyOnFailureTestExecutionListener@5656be13, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverTestExecutionListener@4218d6a3]
17:24:42.758 [main] DEBUG org.springframework.test.annotation.ProfileValueUtils - Retrieved @ProfileValueSourceConfiguration [null] for test class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.760 [main] DEBUG org.springframework.test.annotation.ProfileValueUtils - Retrieved ProfileValueSource type [class org.springframework.test.annotation.SystemProfileValueSource] for class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.762 [main] DEBUG org.springframework.test.annotation.ProfileValueUtils - Retrieved @ProfileValueSourceConfiguration [null] for test class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.767 [main] DEBUG org.springframework.test.annotation.ProfileValueUtils - Retrieved ProfileValueSource type [class org.springframework.test.annotation.SystemProfileValueSource] for class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.787 [main] DEBUG org.springframework.test.annotation.ProfileValueUtils - Retrieved @ProfileValueSourceConfiguration [null] for test class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.788 [main] DEBUG org.springframework.test.annotation.ProfileValueUtils - Retrieved ProfileValueSource type [class org.springframework.test.annotation.SystemProfileValueSource] for class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.862 [main] DEBUG org.springframework.test.context.support.AbstractDirtiesContextTestExecutionListener - Before test class: context [DefaultTestContext@4afcd809 testClass = ExampleApplicationTests, testInstance = [null], testMethod = [null], testException = [null], mergedContextConfiguration = [WebMergedContextConfiguration@175c2241 testClass = ExampleApplicationTests, locations = '{}', classes = '{class theo.jpa.demo.ExampleApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true}', contextCustomizers = set[org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@1fc2b765, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@22eeefeb, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer@10a035a0, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@31f924f5], resourceBasePath = 'src/main/webapp', contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.web.ServletTestExecutionListener.activateListener' -> true]], class annotated with @DirtiesContext [false] with mode [null].
17:24:42.870 [main] DEBUG org.springframework.test.annotation.ProfileValueUtils - Retrieved @ProfileValueSourceConfiguration [null] for test class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.870 [main] DEBUG org.springframework.test.annotation.ProfileValueUtils - Retrieved ProfileValueSource type [class org.springframework.test.annotation.SystemProfileValueSource] for class [theo.jpa.demo.ExampleApplicationTests]
17:24:42.961 [main] DEBUG org.springframework.test.context.support.TestPropertySourceUtils - Adding inlined properties to environment: {spring.jmx.enabled=false, org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true, server.port=-1}
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.1.RELEASE)
2019-01-03 17:24:58.582 INFO 1289 --- [ main] theo.jpa.demo.ExampleApplicationTests : Starting ExampleApplicationTests on Theodosioss-MacBook-Pro.local with PID 1289 (started by theodosiostziomakas in /Users/theodosiostziomakas/Desktop/Java Spring Tutorials/spring-boot-spring-mvc-bootstrap)
2019-01-03 17:24:58.584 INFO 1289 --- [ main] theo.jpa.demo.ExampleApplicationTests : No active profile set, falling back to default profiles: default
2019-01-03 17:24:59.422 INFO 1289 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data repositories in DEFAULT mode.
2019-01-03 17:24:59.475 INFO 1289 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 23ms. Found 0 repository interfaces.
2019-01-03 17:24:59.955 INFO 1289 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration' of type [org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration$$EnhancerBySpringCGLIB$$819e6851] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2019-01-03 17:25:00.261 INFO 1289 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2019-01-03 17:25:00.841 INFO 1289 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
2019-01-03 17:25:00.931 INFO 1289 --- [ main] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [
name: default
...]
2019-01-03 17:25:01.090 INFO 1289 --- [ main] org.hibernate.Version : HHH000412: Hibernate Core {5.3.7.Final}
2019-01-03 17:25:01.092 INFO 1289 --- [ main] org.hibernate.cfg.Environment : HHH000206: hibernate.properties not found
2019-01-03 17:25:01.346 INFO 1289 --- [ main] o.hibernate.annotations.common.Version : HCANN000001: Hibernate Commons Annotations {5.0.4.Final}
2019-01-03 17:25:01.547 INFO 1289 --- [ main] org.hibernate.dialect.Dialect : HHH000400: Using dialect: org.hibernate.dialect.MySQL5Dialect
2019-01-03 17:25:01.884 INFO 1289 --- [ main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
2019-01-03 17:25:02.823 INFO 1289 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2019-01-03 17:25:02.903 WARN 1289 --- [ main] aWebConfiguration$JpaWebMvcConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
2019-01-03 17:25:03.305 INFO 1289 --- [ main] theo.jpa.demo.ExampleApplicationTests : Started ExampleApplicationTests in 20.327 seconds (JVM running for 22.223)
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 21.899 s - in theo.jpa.demo.ExampleApplicationTests
2019-01-03 17:25:03.437 INFO 1289 --- [ Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor'
2019-01-03 17:25:03.438 INFO 1289 --- [ Thread-2] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2019-01-03 17:25:03.440 INFO 1289 --- [ Thread-2] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown initiated...
2019-01-03 17:25:03.478 INFO 1289 --- [ Thread-2] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown completed.
[INFO]
[INFO] Results:
[INFO]
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO]
[INFO]
[INFO] --- maven-jar-plugin:3.1.0:jar (default-jar) @ demo ---
[INFO] Building jar: /Users/theodosiostziomakas/Desktop/Java Spring Tutorials/spring-boot-spring-mvc-bootstrap/target/demo-0.0.1-SNAPSHOT.jar
[INFO]
[INFO] --- spring-boot-maven-plugin:2.1.1.RELEASE:repackage (repackage) @ demo ---
[INFO] Replacing main artifact with repackaged archive
[INFO]
[INFO] --- maven-install-plugin:2.5.2:install (default-install) @ demo ---
[INFO] Installing /Users/theodosiostziomakas/Desktop/Java Spring Tutorials/spring-boot-spring-mvc-bootstrap/target/demo-0.0.1-SNAPSHOT.jar to /Users/theodosiostziomakas/.m2/repository/theo/jpa/demo/0.0.1-SNAPSHOT/demo-0.0.1-SNAPSHOT.jar
[INFO] Installing /Users/theodosiostziomakas/Desktop/Java Spring Tutorials/spring-boot-spring-mvc-bootstrap/pom.xml to /Users/theodosiostziomakas/.m2/repository/theo/jpa/demo/0.0.1-SNAPSHOT/demo-0.0.1-SNAPSHOT.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 31.386 s
[INFO] Finished at: 2019-01-03T17:25:05+02:00
[INFO] ------------------------------------------------------------------------
我在问是否有一种方法可以声明一种变量并具有如下所示的内容：
SELECT col1,
col2,
DECODE(
SUM(CASE WHEN col3='A' AND col4='+' THEN col5 ELSE 0 END),
NULL,
0,
SUM(CASE WHEN col3='A' AND col4='+' THEN col5 ELSE 0 END)
)
FROM mytable
group by col1, col2;
答案 0 :(得分：1)
否，但是您可以执行子查询：
SELECT col1,
col2,
DECODE(
SUM(myColumn),
NULL,
0,
SUM(myColumn)
)
FROM (
SELECT
col1,
col2,
CASE WHEN col3='A' AND col4='+' THEN col5 ELSE 0 END myColumn
FROM mytable
) a
group by col1, col2;
答案 1 :(得分：0)
是的，您可以使用替换变量：
SELECT col1,
col2,
DECODE(
&&myVariable,
NULL,
0,
&&myVariable
)
FROM mytable
group by col1, col2;
答案 2 :(得分：0)
您可以简单地使用coalesce()（或nvl()）代替decode()。
SELECT col1,
col2,
coalesce(sum(CASE
WHEN col3 = 'A'
AND col4 = '+' THEN
col5
ELSE
0
END),
0)
FROM mytable
GROUP BY col1,
col2;
答案 3 :(得分：0)
您可以使用coalesce()。我认为这已经足够了：
select col1, col2,
coalesce(sum(case when col3 = 'A' and col4 = '+' then col5 end), 0)
from mytable
group by col1, col2;
实际上，此表达式：
sum(case when col3 = 'A' and col4 = '+' then col5 else 0 end)
在带有NULL的查询中无法返回group by －每个组至少有一行，并且else保证返回0而不是{{1} }。
所以，这也应该做您想要的：
NULL