concat 函数

concat()和concat_ws()函数返回一个或多个字符串连接产生的字符串。

concat() 函数

concat()函数至少需要两个或以上字符串参数，并将所有参数连接成一个字符串。

• 如果字符串参数只有一个，则返回该字符串参数本身。

• 如果任何一个的字符串参数为 NULL，则 concat() 函数返回值为NULL。

语法

concat(string1,string2,...)

示例

//连接 1，2，3
nebula> RETURN concat("1","2","3") AS r;
+-------+
| r     |
+-------+
| "123" |
+-------+

//字符串参数有 NULL
nebula> RETURN concat("1","2",NULL) AS r;
+----------+
| r        |
+----------+
| __NULL__ |
+----------+

nebula> GO FROM "player100" over follow \
        YIELD concat(src(edge), properties($^).age, properties($$).name, properties(edge).degree) AS A;
+------------------------------+
| A                            |
+------------------------------+
| "player10042Tony Parker95"   |
| "player10042Manu Ginobili95" |
+------------------------------+

concat_ws() 函数

concat_ws()函数将两个或以上字符串参数与预定义的分隔符（separator）相连接。

• 如果分隔符为NULL时，concat_ws()函数才返回NULL。

• 如果分隔符不为NULL，字符串参数只有一个，则返回该字符串参数本身。

• 字符串参数存在NULL值时，忽略NULL值，继续连接下一个参数。

语法

concat_ws(separator,string1,string2,... )

示例

//分隔符为+，连接 a，b，c
nebula> RETURN concat_ws("+","a","b","c") AS r;
+---------+
| r       |
+---------+
| "a+b+c" |
+---------+

//分隔符为 NULL
neubla> RETURN concat_ws(NULL,"a","b","c") AS r;
+----------+
| r        |
+----------+
| __NULL__ |
+----------+

//分隔符为+，字符串参数有 NULL
nebula> RETURN concat_ws("+","a",NULL,"b","c") AS r;
+---------+
| r       |
+---------+
| "a+b+c" |
+---------+

//分隔符为+。字符串参数只有一个
nebula> RETURN concat_ws("+","a") AS r;
+-----+
| r   |
+-----+
| "a" |
+-----+

nebula> GO FROM "player100" over follow \
        YIELD concat_ws(" ",src(edge), properties($^).age, properties($$).name, properties(edge).degree) AS A;
+---------------------------------+
| A                               |
+---------------------------------+
| "player100 42 Tony Parker 95"   |
| "player100 42 Manu Ginobili 95" |
+---------------------------------+

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最后更新: March 7, 2023