而只有单个空格的字符串是不会被转成NULL的。因为它并不是空字符串(empty string) postgresql中的NULLs和空字符串(empty string) 使用相同的表结构 postgres@=#SELECT id,content,postgres-# CASE WHEN content IS NULL THEN 1 ELSE 0 END AS isnull,postgres-# CASE WHEN content = '' THEN 1 ELSE 0 END...
as expected. If we look at the first two, the NULL we inserted is still considered a NULL and can't be compared to an empty string. But when we look at the empty string that we inserted for the 2nd row, we don't have a NULL value, we still have an empty string. No conversion...
Certainly “” is correctly treated as the empty string, nothing between two commas is also treated as the empty string, and NULL is treated as the string “NULL”, I think. I believe MySQL uses \N as the representation of a NULL in a text file to be imported, but I don’t know i...
plsql_emptystring_to_blank 布尔 session 级 on/off PLSQL 中空串仍然是空串,不会转换成 null,默认 on。 profile_password_limit 布尔 session 级(superuser) on/off 是否启用密码限制,默认 off。 profile_resource_limit 布尔 session 级(superuser) ...
3、连接字符串中含有空值会把NULL作为 EMPTY STRING declare v_deptno dept.deptno%type; v_loc dept.loc%type; V_FLAG BOOLEAN ; V_REC BOOLEAN :=FALSE; --此值改为TRUE、NULL、FALSE进行不同的比较 V_AVA BOOLEAN:=NULL; begin V_FLAG:=V_REC AND V_AVA; ...
(Node *) n; } | /*EMPTY*/ { $$ = NULL; } ; OptTableFuncElementList: TableFuncElementList { $$ = $1; } | /*EMPTY*/ { $$ = NIL; } ; TableFuncElementList: TableFuncElement { $$ = list_make1($1); } | TableFuncElementList ',' TableFuncElement { $$ = lappend($1, ...
* * alias is an Alias node representing the AS alias-clause attached to the * FROM expression, or NULL if no clause. * * eref is the table reference name and column reference names (either * real or aliases). Note that system columns (OID etc) are not included * in the column ...
1、raw_parser作为高层入口 2、raw_parser初始化后,通过base_yyparse进入yacc框架 3、yacc框架中调用base_yylex进入lex拿一个token(正常用框架是每次拿一个,PG通过对lex函数的封装可以拿后面多个,有些语法需要看到后面多个一块解析) 4、拿回来token后,...
以字符串输出: SELECT array_to_string(ARRAY[1,2,null], ',', '0') // 第二参数为分隔符,第三个为替换null的数 1.6.2 操作符 1.7 范围类型 int4range int8range numrange tsrange : 不带时区的timestamp范围类型 tstzrange: 带时区的timestamp范围类型 ...
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...