所以结论是:按照效率排序的话,count(字段)<count(主键id)<count(1)≈count(*),所以尽量使用count(*)就行了。 2 优化COUNT()查询 如果COUNT()的括号中定义了列名或其它表达式,COUNT就会统计这个表达式有值的次数,不会统计Null。 COUNT的另一种形式就是统计结果中行的数量,当MySql知道括号中的表达式永远都不会为...
_pool_count-1]; u2 access_flags; u2 this_class; u2 super_class; u2 interfaces_count; u2 interfaces[interfaces_count]; u2 fields_count; field_info fields[fields_count]; u2 methods_count; method_info methods[methods_count]; u2 attribute_count; attributes_info; attributes[attributes_count]; ...
}else{try{//(9)blockingQueue.put(eventObject); }catch(InterruptedException e) {//Interruption of current thread when in doAppend method should notbe consumed//by AsyncAppenderThread.currentThread().interrupt(); } } } 如果neverBlock 被设置为false(默认为false)则会调用阻塞队列的put方法,而put 是阻...
Array.prototype.count =function(){returnthis.length; }; Javascript Array count() letnumbers = [1,2,3,4];letmoreNumbers = newArray(1,2,3,4);Array.prototype.count =function() {returnthis.length; } console.log(numbers.count());//www.java2s.comconsole.log(moreNumbers.count()); ...
int lastRet = -1; // 代表上一个要访问的元素下标 int expectedModCount = modCount;//代表...
JavaObjectArray<T> JavaObjectExtensions JavaPeerableExtensions JavaPrimitiveArray<T> JavaSByteArray JavaSingleArray JavaTypeParametersAttribute JniAddNativeMethodRegistrationAttribute JniArgumentValue JniArrayElements JniBooleanArrayElements JniCharArrayElements ...
This method frees theArrayobject and releases the resources that it holds. ObjectgetArray() Retrieves the contents of the SQLARRAYvalue designated by thisArrayobject in the form of an array in the Java programming language. ObjectgetArray(long index, int count) ...
JavaArray<T> 属性 方法 显式接口实现 JavaBooleanArray JavaCharArray JavaDoubleArray JavaException JavaInt16Array JavaInt32Array JavaInt64Array JavaInterfaceDefaultMethodAttribute JavaLibraryReferenceAttribute JavaObject JavaObjectArray<T> JavaObjectExtensions JavaPeerableExtensions JavaPrimitiveArray<T> JavaSByt...
public java.lang.StringdescType() throws java.sql.SQLException Describe the collection type. Returns: the type information Throws: java.sql.SQLException Since: 8.1.7 toResultSet public java.sql.ResultSettoResultSet(ARRAYarray, long index, int count, java.util.Map map, boolean saveLocalCopy) thr...
Retrieves a slice of the SQLARRAYvalue designated by thisArrayobject, beginning with the specifiedindexand containing up tocountsuccessive elements of the SQL array. This method uses the type map associated with the connection for customizations of the type mappings. ...