Postgres 11 | db<>fiddle

SELECT upper('é' collate "C") AS "C", upper('é' collate "C.UTF-8") AS "C.UTF-8", upper('é' collate "ucs_basic") AS "ucs_basic";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: SELECT upper('é' collate "C") AS "C", upper('é' collate "C.U... ^

hidden batch(es)

SELECT 'A' AS "0041", E'\u0378' AS "0378", ('A' < E'\u0378' collate "C") AS "C", ('A' < E'\u0378' collate "C.UTF-8") AS "C.UTF-8", ('A' < E'\u0378' collate "ucs_basic") AS "ucs_basic", ('A' < E'\u0378' collate "en_GB") AS "en_GB";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: ...< E'\u0378' collate "C") AS "C", ('A' < E'\u0378' collate "C... ^

hidden batch(es)

SELECT E'\u0379' AS "0379", E'\u0378' AS "0378", (E'\u0379' < E'\u0378' collate "C") AS "C", (E'\u0379' < E'\u0378' collate "C.UTF-8") AS "C.UTF-8", (E'\u0379' < E'\u0378' collate "ucs_basic") AS "ucs_basic", (E'\u0379' < E'\u0378' collate "en_GB") AS "en_GB";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: ...0378' collate "C") AS "C", (E'\u0379' < E'\u0378' collate "C... ^

hidden batch(es)

SELECT E'\u0020' AS "0020", E'\u0378' AS "0378", (E'\u0020' < E'\u0378' collate "C") AS "C", (E'\u0020' < E'\u0378' collate "C.UTF-8") AS "C.UTF-8", (E'\u0020' < E'\u0378' collate "ucs_basic") AS "ucs_basic", (E'\u0020' < E'\u0378' collate "en_GB") AS "en_GB";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: ...0378' collate "C") AS "C", (E'\u0020' < E'\u0378' collate "C... ^

hidden batch(es)

SELECT E'\u0001' AS "0001", E'\u0378' AS "0378", (E'\u0001' < E'\u0378' collate "C") AS "C", (E'\u0001' < E'\u0378' collate "C.UTF-8") AS "C.UTF-8", (E'\u0001' < E'\u0378' collate "ucs_basic") AS "ucs_basic", (E'\u0001' < E'\u0378' collate "en_GB") AS "en_GB";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: ...0378' collate "C") AS "C", (E'\u0001' < E'\u0378' collate "C... ^

hidden batch(es)

SELECT 'A' AS "0041", E'\u0377' AS "0377", ('A' < E'\u0377' collate "C") AS "C", ('A' < E'\u0377' collate "C.UTF-8") AS "C.UTF-8", ('A' < E'\u0377' collate "ucs_basic") AS "ucs_basic", ('A' < E'\u0377' collate "en_GB") AS "en_GB";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: ...< E'\u0377' collate "C") AS "C", ('A' < E'\u0377' collate "C... ^

hidden batch(es)

SELECT E'\u00E9' AS "00E9", E'\u00D3' AS "00D3", (E'\u00E9' < E'\u00D3' collate "C") AS "C", (E'\u00E9' < E'\u00D3' collate "C.UTF-8") AS "C.UTF-8", (E'\u00E9' < E'\u00D3' collate "ucs_basic") AS "ucs_basic", (E'\u00E9' < E'\u00D3' collate "en_GB") AS "en_GB";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: ...00D3' collate "C") AS "C", (E'\u00E9' < E'\u00D3' collate "C... ^

hidden batch(es)

SELECT E'\u0510' AS "0510", E'\u08BA' AS "08BA", (E'\u0510' < E'\u08BA' collate "C") AS "C", (E'\u0510' < E'\u08BA' collate "C.UTF-8") AS "C.UTF-8", (E'\u0510' < E'\u08BA' collate "ucs_basic") AS "ucs_basic", (E'\u0510' < E'\u08BA' collate "en_GB") AS "en_GB";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: ...08BA' collate "C") AS "C", (E'\u0510' < E'\u08BA' collate "C... ^

hidden batch(es)

SELECT ('ab' < 'a-c' collate "C") AS "C", ('ab' < 'a-c' collate "C.UTF-8") AS "C.UTF-8", ('ab' < 'a-c' collate "ucs_basic") AS "ucs_basic", ('ab' < 'a-c' collate "en_GB") AS "en_GB";

ERROR: collation "C.UTF-8" for encoding "UTF8" does not exist LINE 1: ... ('ab' < 'a-c' collate "C") AS "C", ('ab' < 'a-c' collate "C... ^

hidden batch(es)

select * from pg_collation where collprovider='c' order by "collname";

collname	collnamespace	collowner	collprovider	collencoding	collcollate	collctype
C	11	10	c	-1	C	C
C.utf8	11	10	c	6	C.utf8	C.utf8
POSIX	11	10	c	-1	POSIX	POSIX
en_AG	11	10	c	6	en_AG	en_AG
en_AU	11	10	c	6	en_AU.utf8	en_AU.utf8
en_AU	11	10	c	8	en_AU	en_AU
en_AU.utf8	11	10	c	6	en_AU.utf8	en_AU.utf8
en_BW	11	10	c	8	en_BW	en_BW
en_BW	11	10	c	6	en_BW.utf8	en_BW.utf8
en_BW.utf8	11	10	c	6	en_BW.utf8	en_BW.utf8
en_CA	11	10	c	6	en_CA.utf8	en_CA.utf8
en_CA	11	10	c	8	en_CA	en_CA
en_CA.utf8	11	10	c	6	en_CA.utf8	en_CA.utf8
en_DK	11	10	c	8	en_DK	en_DK
en_DK	11	10	c	6	en_DK.utf8	en_DK.utf8
en_DK.utf8	11	10	c	6	en_DK.utf8	en_DK.utf8
en_GB	11	10	c	8	en_GB	en_GB
en_GB	11	10	c	16	en_GB.iso885915	en_GB.iso885915
en_GB	11	10	c	6	en_GB.utf8	en_GB.utf8
en_GB.iso885915	11	10	c	16	en_GB.iso885915	en_GB.iso885915
en_GB.utf8	11	10	c	6	en_GB.utf8	en_GB.utf8
en_HK	11	10	c	8	en_HK	en_HK
en_HK	11	10	c	6	en_HK.utf8	en_HK.utf8
en_HK.utf8	11	10	c	6	en_HK.utf8	en_HK.utf8
en_IE	11	10	c	8	en_IE	en_IE
en_IE	11	10	c	6	en_IE.utf8	en_IE.utf8
en_IE.utf8	11	10	c	6	en_IE.utf8	en_IE.utf8
en_IE@euro	11	10	c	16	en_IE@euro	en_IE@euro
en_IL	11	10	c	6	en_IL	en_IL
en_IN	11	10	c	6	en_IN	en_IN
en_NG	11	10	c	6	en_NG	en_NG
en_NZ	11	10	c	6	en_NZ.utf8	en_NZ.utf8
en_NZ	11	10	c	8	en_NZ	en_NZ
en_NZ.utf8	11	10	c	6	en_NZ.utf8	en_NZ.utf8
en_PH	11	10	c	6	en_PH.utf8	en_PH.utf8
en_PH	11	10	c	8	en_PH	en_PH
en_PH.utf8	11	10	c	6	en_PH.utf8	en_PH.utf8
en_SC	11	10	c	6	en_SC.utf8	en_SC.utf8
en_SC.utf8	11	10	c	6	en_SC.utf8	en_SC.utf8
en_SG	11	10	c	6	en_SG.utf8	en_SG.utf8
en_SG	11	10	c	8	en_SG	en_SG
en_SG.utf8	11	10	c	6	en_SG.utf8	en_SG.utf8
en_US	11	10	c	6	en_US.utf8	en_US.utf8
en_US	11	10	c	16	en_US.iso885915	en_US.iso885915
en_US	11	10	c	8	en_US	en_US
en_US.iso885915	11	10	c	16	en_US.iso885915	en_US.iso885915
en_US.utf8	11	10	c	6	en_US.utf8	en_US.utf8
en_ZA	11	10	c	8	en_ZA	en_ZA
en_ZA	11	10	c	6	en_ZA.utf8	en_ZA.utf8
en_ZA.utf8	11	10	c	6	en_ZA.utf8	en_ZA.utf8
en_ZM	11	10	c	6	en_ZM	en_ZM
en_ZW	11	10	c	8	en_ZW	en_ZW
en_ZW	11	10	c	6	en_ZW.utf8	en_ZW.utf8
en_ZW.utf8	11	10	c	6	en_ZW.utf8	en_ZW.utf8
ucs_basic	11	10	c	6	C	C
…

hidden batch(es)