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¶
bash
concat(string1,string2,...)
示例¶
```bash //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¶
bash
concat_ws(separator,string1,string2,... )
示例¶
```bash //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" | +---------------------------------+ ```