正则表达式 – 正则表达式中的运算符优先级

Table 4-2 lists the list of metacharacters supported for use in regular expressions passed to SQL regular expression functions and conditions. These metacharacters conform to the POSIX standard; any differences in behavior from the standard are noted in the “Description” column.

并看看|该表中的值：

The expression a|b matches character a or character b.

再加上看看POSIX doc：

Operator precedence
The order of precedence for of operators is as follows:

1. Collation-related bracket symbols [==] [::] [..]

2. Escaped characters

3. Character set (bracket expression) []

4. Grouping ()

5. Single-character-ERE duplication * + ? {m,n}

6. Concatenation

7. Anchoring ^$

8. Alternation |

我会说H | ha与(？：H | ha)相同.