GREATEST¶

语法¶

GREATEST( <expr1> [ , <expr2> ... ] )

实参¶

exprN

实参必须包含至少一个表达式。所有表达式都应为相同类型或兼容的类型。

返回¶

• 第一个实参确定返回类型：

  • 如果第一种类型是数值，则返回类型将根据所有实参列表中的数值类型“扩宽”。

  • 如果第一种类型不是数值，则所有其他实参必须可转换为第一种类型。

排序规则详细信息¶

• The collation specifications of all input arguments must be compatible.

• The comparisons follow the collation based on the input arguments' collations and precedences.

• The collation of the result of the function is the highest-precedence collation of the inputs.

示例¶

基本示例：

CREATE TABLE test_table_1_greatest (col_1 INTEGER, col_2 INTEGER, 
    col_3 INTEGER, col_4 FLOAT);
INSERT INTO test_table_1_greatest (col_1, col_2, col_3, col_4) VALUES
    (1, 2,    3,  4.00),
    (2, 4,   -1, -2.00),
    (3, 6, NULL, 13.45);

Copy

SELECT
       col_1,
       col_2,
       col_3,
       GREATEST(col_1, col_2, col_3) AS greatest
   FROM test_table_1_greatest
   ORDER BY col_1;

Copy

+-------+-------+-------+----------+
| COL_1 | COL_2 | COL_3 | GREATEST |
|-------+-------+-------+----------|
|     1 |     2 |     3 |        3 |
|     2 |     4 |    -1 |        4 |
|     3 |     6 |  NULL |     NULL |
+-------+-------+-------+----------+

SELECT
       col_1,
       col_4,
       GREATEST(col_1, col_4) AS greatest
   FROM test_table_1_greatest
   ORDER BY col_1;

Copy

+-------+-------+----------+
| COL_1 | COL_4 | GREATEST |
|-------+-------+----------|
|     1 |  4    |     4    |
|     2 | -2    |     2    |
|     3 | 13.45 |    13.45 |
+-------+-------+----------+