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update doc

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taiyang-li 2024-07-02 09:54:37 +08:00
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docs/en/sql-reference/functions/string-functions.md
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@ -571,6 +571,7 @@ SELECT upper('clickhouse');
Converts a string to lowercase, assuming that the string contains valid UTF-8 encoded text. If this assumption is violated, no exception is thrown and the result is undefined.
Does not detect the language, e.g. for Turkish the result might not be exactly correct (i/İ vs. i/I).
If the length of the UTF-8 byte sequence is different for upper and lower case of a code point, the result may be incorrect for this code point.
@ -734,13 +735,13 @@ concat(s1, s2, ...)
**Arguments**
Values of arbitrary type. Empty argument is also allowed.
Values of arbitrary type.
Arguments which are not of types [String](../data-types/string.md) or [FixedString](../data-types/fixedstring.md) are converted to strings using their default serialization. As this decreases performance, it is not recommended to use non-String/FixedString arguments.
**Returned values**
The String created by concatenating the arguments. If there are no arguments, the function returns empty string.
The String created by concatenating the arguments.
If any of arguments is `NULL`, the function returns `NULL`.