array_count
array_count
description
array_count(lambda, array1, ...)使用 lambda 表达式作为输入参数，对其他输入 ARRAY 参数的内部数据进行相应的表达式计算。返回使得 lambda(array1[i], ...) 返回值不为 0 的元素数量。如果找不到到满足此条件的元素，则返回 0。
lambda 表达式中输入的参数为 1 个或多个，必须和后面输入的数组列数一致，且所有输入的 array 的元素个数必须相同。在 lambda 中可以执行合法的标量函数，不支持聚合函数等。
array_count(x->x, array1);
array_count(x->(x%2 = 0), array1);
array_count(x->(abs(x)-1), array1);
array_count((x,y)->(x = y), array1, array2);example
mysql> select array_count(x -> x, [0, 1, 2, 3]);
+--------------------------------------------------------+
| array_count(array_map([x] -> x(0), ARRAY(0, 1, 2, 3))) |
+--------------------------------------------------------+
| 3 |
+--------------------------------------------------------+
1 row in set (0.00 sec)
mysql> select array_count(x -> x > 2, [0, 1, 2, 3]);
+------------------------------------------------------------+
| array_count(array_map([x] -> x(0) > 2, ARRAY(0, 1, 2, 3))) |
+------------------------------------------------------------+
| 1 |
+------------------------------------------------------------+
1 row in set (0.01 sec)
mysql> select array_count(x -> x is null, [null, null, null, 1, 2]);
+----------------------------------------------------------------------------+
| array_count(array_map([x] -> x(0) IS NULL, ARRAY(NULL, NULL, NULL, 1, 2))) |
+----------------------------------------------------------------------------+
| 3 |
+----------------------------------------------------------------------------+
1 row in set (0.01 sec)
mysql> select array_count(x -> power(x,2)>10, [1, 2, 3, 4, 5]);
+------------------------------------------------------------------------------+
| array_count(array_map([x] -> power(x(0), 2.0) > 10.0, ARRAY(1, 2, 3, 4, 5))) |
+------------------------------------------------------------------------------+
| 2 |
+------------------------------------------------------------------------------+
1 row in set (0.01 sec)
mysql> select *, array_count((x, y) -> x>y, c_array1, c_array2) from array_test;
+------+-----------------+-------------------------+-----------------------------------------------------------------------+
| id | c_array1 | c_array2 | array_count(array_map([x, y] -> x(0) > y(1), `c_array1`, `c_array2`)) |
+------+-----------------+-------------------------+-----------------------------------------------------------------------+
| 1 | [1, 2, 3, 4, 5] | [10, 20, -40, 80, -100] | 2 |
| 2 | [6, 7, 8] | [10, 12, 13] | 0 |
| 3 | [1] | [-100] | 1 |
| 4 | [1, NULL, 2] | [NULL, 3, 1] | 1 |
| 5 | [] | [] | 0 |
| 6 | NULL | NULL | 0 |
+------+-----------------+-------------------------+-----------------------------------------------------------------------+
6 rows in set (0.02 sec)
keywords
ARRAY, COUNT, ARRAY_COUNT