Postgres 11

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SELECT E'TAB\x9TAB' AS "Single Byte", E'\xF0\x9F\x91\xBE' AS "UTF-8 bytes";

Single Byte
UTF-8 bytes

TAB	TAB
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SELECT 1

SELECT E'\u0F02' AS "Code Point",
       E'\uD83D\uDC7E' AS "UTF-16 Surrogate Pair",
       E'\U0000D83D\U0000DC7E' AS "UTF-16 Surrogate Pair via UTF-32",
       E'\U0001F47E' AS "UTF-32";

Code Point
UTF-16 Surrogate Pair
UTF-16 Surrogate Pair via UTF-32
UTF-32

༂
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SELECT 1

SELECT E'\U0010FFFF' AS "Highest UTF-32 Code Point";

Highest UTF-32 Code Point

􏿿

SELECT 1

SELECT E'\U00110000' AS "1 Value Higher Than Highest UTF-32 Code Point is Invalid";

ERROR:  invalid Unicode escape value at or near "E'\U00110000"
LINE 1: SELECT E'\U00110000' AS "1 Value Higher Than Highest UTF-32 ...
               ^

SELECT U&'\0F02' AS "Code Point",
       U&'\D83D\DC7E' AS "UTF-16 Surrogate Pair",
       U&'\+00D83D\+00DC7E' AS "UTF-16 Surrogate Pair via UTF-32",
       U&'\+01F47E' AS "UTF-32";

Code Point
UTF-16 Surrogate Pair
UTF-16 Surrogate Pair via UTF-32
UTF-32

༂
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👾
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SELECT 1