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How to filter out rows with given column(not null)?

由 旧时模样 提交于 2020-01-23 06:08:13
问题 I want to do a hbase scan with filters. For example, my table has column family A,B,C, and A has a column X. Some rows have the column X and some do not. How can I implement the filter to filter out all the rows with column X? 回答1: I guess you are looking for SingleColumnValueFilter in HBase. As mentioned in the API To prevent the entire row from being emitted if the column is not found on a row, use setFilterIfMissing(boolean) on Filter object. Otherwise, if the column is found, the entire

Can MySQL INT type be non-zero NULL

由 旧城冷巷雨未停 提交于 2020-01-23 04:43:52
问题 I'm creating a MySQL DB which is composed of weekly data sets, going back for the past decade. There are some data points which exist for recent records, but which were not tracked in some of the older data sets. The fields in question all contain integer values, and '0' is a perfectly valid (and frequent) value for the records which did track the data points. I need to be able to distinguish between a value of zero and non-existent data. Therefore, I need to find out if it is possible to

Throw an exception or return null

由 丶灬走出姿态 提交于 2020-01-22 21:29:50
问题 If I've got the function below, with two choices private MyObject findBlank() { for (int i = 0; i < pieces.length; i++) { if(pieces[i].isBlank()){ return pieces[i]; } } return null; } private MyObject findBlank() { for (int i = 0; i < pieces.length; i++) { if(pieces[i].isBlank()){ return pieces[i]; } } throw new NoSuchFieldError("No blank piece found!"); } From this method I know that it should always return an object one of the 'pieces' always is isBlank() == true , the return null at the

How to count null values in postgresql?

由 a 夏天 提交于 2020-01-22 02:33:05
问题 select distinct "column" from table; output: column 1 0.0 2 [null] 3 1.0 But when I try to count the null values select count("column") from train where "column" is NULL; Gives output 0 (zero) Can you suggest where it's going wrong? 回答1: Use count(*) : select count(*) from train where "column" is NULL; count() with any other argument counts the non-NULL values, so there are none if "column" is NULL . 来源： https://stackoverflow.com/questions/53934294/how-to-count-null-values-in-postgresql

IE11 - Variable is out of range even though I used `let` for the loop

由 你。 提交于 2020-01-21 12:07:12
问题 The console stops on this line with the error: Unable to get property 'srcset' of undefined or null reference var srcObj = rollOverCollectionA[i].srcset.splice(171, 0, '-hover'); This above line is part of this section. document.addEventListener("DOMContentLoaded", function (event) { var rollOverCollectionA = document.getElementById("roll-over-collection-b").getElementsByClassName("rollover"); rollOverCollectionA = Array.prototype.slice.apply(rollOverCollectionA); console.log(

Is segfault guaranteed when dereferencing null pointer (C/C++)

由 依然范特西╮ 提交于 2020-01-21 08:35:29
问题 In the C/C++ code below int * a = malloc(N * sizeof(int)); // suppose return value is NULL a[2] = 1; In the case where malloc returns NULL , do I have a guarantee that segfault will occur or is the behavior unpredictable? 回答1: In a word, no. To quote from Wikipedia: Dereferencing the NULL pointer typically results in an attempted read or write from memory that is not mapped - triggering a segmentation fault or access violation. This may represent itself to the developer as a program crash, or

Why is null stored as a string in localStorage?

由 删除回忆录丶 提交于 2020-01-21 08:30:45
问题 In the Chrome console I set foo to null: localStorage.setItem("foo",null) Then I test, whether it is null: console.log(localStorage.getItem("foo")==null) prints false . Then I test, whether it is the string "null" : console.log(localStorage.getItem("foo")=="null") prints true . I thought that null was a legitimate Javascript value. Storing it as the string "null" is very counter intuitive and caused a strange bug in an otherwise working program, when I cleared the localStorage in the browser

Why is null stored as a string in localStorage?

由 纵饮孤独 提交于 2020-01-21 08:28:28
问题 In the Chrome console I set foo to null: localStorage.setItem("foo",null) Then I test, whether it is null: console.log(localStorage.getItem("foo")==null) prints false . Then I test, whether it is the string "null" : console.log(localStorage.getItem("foo")=="null") prints true . I thought that null was a legitimate Javascript value. Storing it as the string "null" is very counter intuitive and caused a strange bug in an otherwise working program, when I cleared the localStorage in the browser

Linux C用http协议下载文件

由 醉酒当歌 提交于 2020-01-21 07:54:19
#include <stdio.h> #include <stdlib.h> #include <limits.h> #include <sys/time.h> #include <sys/select.h> #include <netdb.h> #include <ctype.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <unistd.h> #include <netinet/in.h> #define RECV_BUF_LEN (1024*100) struct hostent *host; char domain[256] = {0}; int port = 0; int ret_status(char *recv_buf) { if(NULL == recv_buf) { printf("recv_buf is NULL\n"); return -1; } int http_status = 0; char line[256] = {0} ; char *rest ; rest = strstr(recv_buf,"\r\n"); if ( rest != NULL) { memcpy(line,recv_buf,rest

236. 二叉树的最近公共祖先(java)

由 自作多情 提交于 2020-01-21 05:01:42
给定一个二叉树, 找到该树中两个指定节点的最近公共祖先。 百度百科中最近公共祖先的定义为：“对于有根树 T 的两个结点 p、q，最近公共祖先表示为一个结点 x，满足 x 是 p、q 的祖先且 x 的深度尽可能大（一个节点也可以是它自己的祖先）。” 例如，给定如下二叉树: root = [3,5,1,6,2,0,8,null,null,7,4] 示例 1: 输入: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1 输出: 3 解释: 节点 5 和节点 1 的最近公共祖先是节点 3。 示例 2: 输入: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4 输出: 5 解释: 节点 5 和节点 4 的最近公共祖先是节点 5。因为根据定义最近公共祖先节点可以为节点本身。 说明: 所有节点的值都是唯一的。 p、q 为不同节点且均存在于给定的二叉树中。 来源：力扣（LeetCode） 链接：https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。 /** * Definition for a binary tree node. *
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