NULL值表示一个未知数据或者一个空值,算术操作符的任何一个操作数为NULL值,结果均为提个NULL值,这个规则也适合很多函数,只有CONCAT,DECODE,DUMP,NVL,REPLACE在调用了NULL参数时能够返回非NULL值。在这些中NVL函数时最重要的,因为他能直接处理NULL值,NVL有两个参数:NVL(x1,x2),x1和x2都是表达式,当x1为null时返...
3.1 redis主节点 # 先手动配置redis-vip地址ifconfig eth0:3 192.168.150.187/24# 安装包下载地址http://download.redis.io/releases/# 下载[root@master ~]# wget http://download.redis.io/releases/redis-6.2.9.tar.gz2、 安装gcc[root@master ~]# yum install -y gcc3、解压[root@master ~]# tar ...
一、判空 StringUtils提供常用的判断空字符串有两个方法:isEmpty和isBlank,这两者的有何区别呢,直接看源码:// isEmpty public static boolean isEmpty(String str) { re Iterator判空java中 java bc 字符串 字符数组 转载 代码工匠传奇 2023-10-09 20:48:13 173阅读 优雅判空 我将1965年发明的 null ...
-gdwarf-version Produce debugging informationinDWARFformat(ifthatissupported). Thisisthe format usedbyDBXonIRIX 6. Thevalueof version may be either 2or3; thedefaultversionis3.Note thatwithDWARF version2some ports require,andwill always use, some non-conflicting DWARF3extensionsinthe unwind tables....
So, COALESCE(field, '') returns the value of field if it's not NULL, and otherwise returns an empty string. When used in COALESCE(field, '') = '' when trying to find any rows where field is "empty", this is basically saying "if field is NULL then use an empty string in its ...
if test "$(id -u)" -eq 0; then cmd= for v in PGSETUP_DEBUG PGSETUP_INITDB_OPTIONS PGSETUP_PGUPGRADE_OPTIONS; do eval var_content=\$$v test -z "$var_content" && continue cmd+=$v="$(printf %q "$var_content") " ...
如成功,则为authenticon ok(0) // case 'R': /* Authentication Request */ if (status == STATUS_OK) sendAuthRequest(port, AUTH_REQ_OK, NULL, 0); // -- parse sendAuthRequest // 类似上面分析的,此处发送的消息类型为authentication request, 但是quthentication request code为AUTH_REQ_OK //...
A null value is treated as an empty string. I treats the argument value as an SQL identifier, double-quoting it if necessary. It is an error for the value to be null (equivalent to quote_ident). L quotes the argument value as an SQL literal. A null value is displayed as the string...
const llvm::FunctionSummary *fs; llvm::StringRef modPath = gvs->modulePath(); llvm::Module *defMod; llvm::Function *funcDef; fs = llvm::cast<llvm::FunctionSummary>(gvs); if ((int) fs->instCount() > inlineState.costLimit) { ilog(DEBUG1, "ineligibile to import %s due to early...
TupIsNull(result)) { /* * If the subplan gave us something then return it as-is. We do * NOT make use of the result slot that was set up in * ExecInitAppend; there's no need for it. */ return result; } // 同步子计划结果为空, // 说明这个同步子计划执行结束,需要选择下一...