{"Entry":{"collection":"type","key":"bool","name":"boolean","aliases":["bool"],"metadata":{"aliases":["bool"],"category":"Boolean","content_hash":"cbb450169ba5c084ef43439d7c0ecedde7b17367cafe9ee0415b302e1b550315","imported_at":"2026-09-30T00:40:35.468082+08:00","name":"boolean","name_zh":"","slug":"bool","summary":"logical Boolean (true/false)"}},"Definition":{"Collection":"type","Key":"bool","SourceDatabase":"center","Version":"18","SourceTable":"data_type","SourceKey":"bool","SourceRevision":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","Facts":{"aliases":["bool"],"casts":[{"castcontext":"e","castfunc":"bool(int4)","castmethod":"f","castsource":"int4","casttarget":"bool"},{"castcontext":"e","castfunc":"int4(bool)","castmethod":"f","castsource":"bool","casttarget":"int4"},{"castcontext":"a","castfunc":"text(bool)","castmethod":"f","castsource":"bool","casttarget":"text"},{"castcontext":"a","castfunc":"text(bool)","castmethod":"f","castsource":"bool","casttarget":"varchar"},{"castcontext":"a","castfunc":"text(bool)","castmethod":"f","castsource":"bool","casttarget":"bpchar"},{"castcontext":"e","castfunc":"bool(jsonb)","castmethod":"f","castsource":"jsonb","casttarget":"bool"}],"catalog":{"array_type_name":"_bool","array_type_oid":"1000","descr":"boolean, format 't'/'f'","oid":"16","typacl":"_null_","typalign":"c","typanalyze":"-","typarray":"0","typbasetype":"0","typbyval":"t","typcategory":"B","typcollation":"0","typdefault":"_null_","typdefaultbin":"_null_","typdelim":"','","typelem":"0","typinput":"boolin","typisdefined":"t","typispreferred":"t","typlen":"1","typmodin":"-","typmodout":"-","typname":"bool","typnamespace":"pg_catalog","typndims":"0","typnotnull":"f","typoutput":"boolout","typowner":"POSTGRES","typreceive":"boolrecv","typrelid":"0","typsend":"boolsend","typstorage":"p","typsubscript":"-","typtype":"b","typtypmod":"-1"},"comparison_data":{"aliases":["bool"],"casts":[{"castcontext":"a","castfunc":"text(bool)","castmethod":"f","castsource":"bool","casttarget":"bpchar"},{"castcontext":"a","castfunc":"text(bool)","castmethod":"f","castsource":"bool","casttarget":"text"},{"castcontext":"a","castfunc":"text(bool)","castmethod":"f","castsource":"bool","casttarget":"varchar"},{"castcontext":"e","castfunc":"bool(int4)","castmethod":"f","castsource":"int4","casttarget":"bool"},{"castcontext":"e","castfunc":"bool(jsonb)","castmethod":"f","castsource":"jsonb","casttarget":"bool"},{"castcontext":"e","castfunc":"int4(bool)","castmethod":"f","castsource":"bool","casttarget":"int4"}],"catalog":{"array_type_name":"_bool","typacl":"_null_","typalign":"c","typanalyze":"-","typarray":"_bool","typbasetype":"0","typbyval":"t","typcategory":"B","typcollation":"0","typdefault":"_null_","typdefaultbin":"_null_","typdelim":",","typelem":"0","typinput":"boolin","typisdefined":"t","typispreferred":"t","typlen":"1","typmodin":"-","typmodout":"-","typname":"bool","typndims":"0","typnotnull":"f","typoutput":"boolout","typreceive":"boolrecv","typrelid":"0","typsend":"boolsend","typstorage":"p","typsubscript":"-","typtype":"b","typtypmod":"-1"},"facts":[{"label":"Catalog name","value":"pg_catalog.bool"},{"label":"Declared length","value":"1 byte"},{"label":"Documented declaration","value":"boolean"},{"label":"Input function","value":"boolin"},{"label":"Output function","value":"boolout"},{"label":"Storage Size","value":"1 byte"},{"label":"Storage strategy","value":"plain"},{"label":"Type OID","value":"16"},{"label":"Type kind","value":"Base type"}],"operator_classes":[{"opcdefault":"t","opcfamily":"btree/bool_ops","opcintype":"bool","opckeytype":"0","opcmethod":"btree","opcname":"bool_ops"},{"opcdefault":"t","opcfamily":"hash/bool_ops","opcintype":"bool","opckeytype":"0","opcmethod":"hash","opcname":"bool_ops"}],"operators":[{"oprcanhash":"f","oprcanmerge":"f","oprcode":"boolge","oprcom":"\u003c=(bool,bool)","oprjoin":"scalargejoinsel","oprkind":"b","oprleft":"bool","oprname":"\u003e=","oprnegate":"\u003c(bool,bool)","oprrest":"scalargesel","oprresult":"bool","oprright":"bool"},{"oprcanhash":"f","oprcanmerge":"f","oprcode":"boolgt","oprcom":"\u003c(bool,bool)","oprjoin":"scalargtjoinsel","oprkind":"b","oprleft":"bool","oprname":"\u003e","oprnegate":"\u003c=(bool,bool)","oprrest":"scalargtsel","oprresult":"bool","oprright":"bool"},{"oprcanhash":"f","oprcanmerge":"f","oprcode":"boolle","oprcom":"\u003e=(bool,bool)","oprjoin":"scalarlejoinsel","oprkind":"b","oprleft":"bool","oprname":"\u003c=","oprnegate":"\u003e(bool,bool)","oprrest":"scalarlesel","oprresult":"bool","oprright":"bool"},{"oprcanhash":"f","oprcanmerge":"f","oprcode":"boollt","oprcom":"\u003e(bool,bool)","oprjoin":"scalarltjoinsel","oprkind":"b","oprleft":"bool","oprname":"\u003c","oprnegate":"\u003e=(bool,bool)","oprrest":"scalarltsel","oprresult":"bool","oprright":"bool"},{"oprcanhash":"f","oprcanmerge":"f","oprcode":"boolne","oprcom":"\u003c\u003e(bool,bool)","oprjoin":"neqjoinsel","oprkind":"b","oprleft":"bool","oprname":"\u003c\u003e","oprnegate":"=(bool,bool)","oprrest":"neqsel","oprresult":"bool","oprright":"bool"},{"oprcanhash":"t","oprcanmerge":"t","oprcode":"booleq","oprcom":"=(bool,bool)","oprjoin":"eqjoinsel","oprkind":"b","oprleft":"bool","oprname":"=","oprnegate":"\u003c\u003e(bool,bool)","oprrest":"eqsel","oprresult":"bool","oprright":"bool"}],"ranges":[]},"comparison_hash":"d2a9de854c70ffc101fdf525d5785cc8d01579400091a1e0b52f8c20cbb49cc5","coverage":"source inventory; exact declared input types for operator classes","description":["logical Boolean (true/false)"],"facts":[{"label":"Catalog name","value":"pg_catalog.bool"},{"label":"Type OID","value":"16"},{"label":"Type kind","value":"Base type"},{"label":"Declared length","value":"1 byte"},{"label":"Storage strategy","value":"plain"},{"label":"Input function","value":"boolin"},{"label":"Output function","value":"boolout"},{"label":"Documented declaration","value":"boolean"},{"label":"Storage Size","value":"1 byte"},{"label":"Manual description","value":"state of true or false"}],"manual_documentation":"dedicated family chapter","manual_html":"\u003cdiv class=\"sect1\" id=\"DATATYPE-BOOLEAN\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch2 class=\"title\"\u003e8.6. Boolean Type \u003c/h2\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003e\u003cspan class=\"productname\"\u003ePostgreSQL\u003c/span\u003e provides the standard SQL type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e; see \u003ca class=\"xref\" href=\"/docs/18/datatype-boolean.html#DATATYPE-BOOLEAN-TABLE\" title=\"Table 8.19. Boolean Data Type\"\u003eTable 8.19\u003c/a\u003e. The \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e type can have several states: \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003etrue\u003c/span\u003e”\u003c/span\u003e, \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003efalse\u003c/span\u003e”\u003c/span\u003e, and a third state, \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003eunknown\u003c/span\u003e”\u003c/span\u003e, which is represented by the SQL null value.\u003c/p\u003e\n\u003cdiv class=\"table\" id=\"DATATYPE-BOOLEAN-TABLE\"\u003e\n\u003cp class=\"title\"\u003e\u003cstrong\u003eTable 8.19. Boolean Data Type\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv class=\"table-contents\"\u003e\n\u003ctable class=\"table\"\u003e\n\n\n\n\n\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eName\u003c/th\u003e\n\u003cth\u003eStorage Size\u003c/th\u003e\n\u003cth\u003eDescription\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"type\"\u003eboolean\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e1 byte\u003c/td\u003e\n\u003ctd\u003estate of true or false\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\u003cbr class=\"table-break\"\u003e\n\u003cp\u003eBoolean constants can be represented in SQL queries by the SQL key words \u003ccode class=\"literal\"\u003eTRUE\u003c/code\u003e, \u003ccode class=\"literal\"\u003eFALSE\u003c/code\u003e, and \u003ccode class=\"literal\"\u003eNULL\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003eThe datatype input function for type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e accepts these string representations for the \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003etrue\u003c/span\u003e”\u003c/span\u003e state:\u003c/p\u003e\n\u003ctable class=\"simplelist\"\u003e\n\u003ctbody\u003e\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003etrue\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003eyes\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003eon\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003e1\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\u003c/table\u003e\n\u003cp\u003eand these representations for the \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003efalse\u003c/span\u003e”\u003c/span\u003e state:\u003c/p\u003e\n\u003ctable class=\"simplelist\"\u003e\n\u003ctbody\u003e\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003efalse\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003eno\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003eoff\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003e0\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\u003c/table\u003e\n\u003cp\u003eUnique prefixes of these strings are also accepted, for example \u003ccode class=\"literal\"\u003et\u003c/code\u003e or \u003ccode class=\"literal\"\u003en\u003c/code\u003e. Leading or trailing whitespace is ignored, and case does not matter.\u003c/p\u003e\n\u003cp\u003eThe datatype output function for type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e always emits either \u003ccode class=\"literal\"\u003et\u003c/code\u003e or \u003ccode class=\"literal\"\u003ef\u003c/code\u003e, as shown in \u003ca class=\"xref\" href=\"/docs/18/datatype-boolean.html#DATATYPE-BOOLEAN-EXAMPLE\" title=\"Example 8.2. Using the boolean Type\"\u003eExample 8.2\u003c/a\u003e.\u003c/p\u003e\n\u003cdiv class=\"example\" id=\"DATATYPE-BOOLEAN-EXAMPLE\"\u003e\n\u003cp class=\"title\"\u003e\u003cstrong\u003eExample 8.2. Using the \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e Type\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv class=\"example-contents\"\u003e\n\u003cpre class=\"programlisting\"\u003eCREATE TABLE test1 (a boolean, b text);\nINSERT INTO test1 VALUES (TRUE, 'sic est');\nINSERT INTO test1 VALUES (FALSE, 'non est');\nSELECT * FROM test1;\n a |    b\n---+---------\n t | sic est\n f | non est\n\nSELECT * FROM test1 WHERE a;\n a |    b\n---+---------\n t | sic est\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003c/div\u003e\u003cbr class=\"example-break\"\u003e\n\u003cp\u003eThe key words \u003ccode class=\"literal\"\u003eTRUE\u003c/code\u003e and \u003ccode class=\"literal\"\u003eFALSE\u003c/code\u003e are the preferred (SQL-compliant) method for writing Boolean constants in SQL queries. But you can also use the string representations by following the generic string-literal constant syntax described in \u003ca class=\"xref\" href=\"/docs/18/sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS-GENERIC\" title=\"4.1.2.7. Constants of Other Types\"\u003eSection 4.1.2.7\u003c/a\u003e, for example \u003ccode class=\"literal\"\u003e'yes'::boolean\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003eNote that the parser automatically understands that \u003ccode class=\"literal\"\u003eTRUE\u003c/code\u003e and \u003ccode class=\"literal\"\u003eFALSE\u003c/code\u003e are of type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e, but this is not so for \u003ccode class=\"literal\"\u003eNULL\u003c/code\u003e because that can have any type. So in some contexts you might have to cast \u003ccode class=\"literal\"\u003eNULL\u003c/code\u003e to \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e explicitly, for example \u003ccode class=\"literal\"\u003eNULL::boolean\u003c/code\u003e. Conversely, the cast can be omitted from a string-literal Boolean value in contexts where the parser can deduce that the literal must be of type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e.\u003c/p\u003e\n\u003c/div\u003e","manual_path":"datatype-boolean.html","operator_classes":[{"opcdefault":"t","opcfamily":"btree/bool_ops","opcintype":"bool","opckeytype":"0","opcmethod":"btree","opcname":"bool_ops","opcnamespace":"pg_catalog","opcowner":"POSTGRES"},{"opcdefault":"t","opcfamily":"hash/bool_ops","opcintype":"bool","opckeytype":"0","opcmethod":"hash","opcname":"bool_ops","opcnamespace":"pg_catalog","opcowner":"POSTGRES"}],"operators":[{"descr":"less than","oid":"58","oprcanhash":"f","oprcanmerge":"f","oprcode":"boollt","oprcom":"\u003e(bool,bool)","oprjoin":"scalarltjoinsel","oprkind":"b","oprleft":"bool","oprname":"\u003c","oprnamespace":"pg_catalog","oprnegate":"\u003e=(bool,bool)","oprowner":"POSTGRES","oprrest":"scalarltsel","oprresult":"bool","oprright":"bool"},{"descr":"greater than","oid":"59","oprcanhash":"f","oprcanmerge":"f","oprcode":"boolgt","oprcom":"\u003c(bool,bool)","oprjoin":"scalargtjoinsel","oprkind":"b","oprleft":"bool","oprname":"\u003e","oprnamespace":"pg_catalog","oprnegate":"\u003c=(bool,bool)","oprowner":"POSTGRES","oprrest":"scalargtsel","oprresult":"bool","oprright":"bool"},{"descr":"not equal","oid":"85","oid_symbol":"BooleanNotEqualOperator","oprcanhash":"f","oprcanmerge":"f","oprcode":"boolne","oprcom":"\u003c\u003e(bool,bool)","oprjoin":"neqjoinsel","oprkind":"b","oprleft":"bool","oprname":"\u003c\u003e","oprnamespace":"pg_catalog","oprnegate":"=(bool,bool)","oprowner":"POSTGRES","oprrest":"neqsel","oprresult":"bool","oprright":"bool"},{"descr":"equal","oid":"91","oid_symbol":"BooleanEqualOperator","oprcanhash":"t","oprcanmerge":"t","oprcode":"booleq","oprcom":"=(bool,bool)","oprjoin":"eqjoinsel","oprkind":"b","oprleft":"bool","oprname":"=","oprnamespace":"pg_catalog","oprnegate":"\u003c\u003e(bool,bool)","oprowner":"POSTGRES","oprrest":"eqsel","oprresult":"bool","oprright":"bool"},{"descr":"less than or 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rel=\"nofollow\"\u003eTable 8.19\u003c/a\u003e. The \u003ccode\u003eboolean\u003c/code\u003e type can have several states: \u003cspan\u003e“\u003cspan\u003etrue\u003c/span\u003e”\u003c/span\u003e, \u003cspan\u003e“\u003cspan\u003efalse\u003c/span\u003e”\u003c/span\u003e, and a third state, \u003cspan\u003e“\u003cspan\u003eunknown\u003c/span\u003e”\u003c/span\u003e, which is represented by the SQL null value.\u003c/p\u003e\n\u003cdiv id=\"DATATYPE-BOOLEAN-TABLE\"\u003e\n\u003cp\u003e\u003cstrong\u003eTable 8.19. Boolean Data Type\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv\u003e\n\u003ctable\u003e\n\n\n\n\n\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eName\u003c/th\u003e\n\u003cth\u003eStorage Size\u003c/th\u003e\n\u003cth\u003eDescription\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003eboolean\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e1 byte\u003c/td\u003e\n\u003ctd\u003estate of true or false\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\u003cbr\u003e\n\u003cp\u003eBoolean constants can be represented in SQL queries by the SQL key words \u003ccode\u003eTRUE\u003c/code\u003e, \u003ccode\u003eFALSE\u003c/code\u003e, and \u003ccode\u003eNULL\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003eThe datatype input function for type \u003ccode\u003eboolean\u003c/code\u003e accepts these string representations for the \u003cspan\u003e“\u003cspan\u003etrue\u003c/span\u003e”\u003c/span\u003e state:\u003c/p\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003etrue\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003eyes\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003eon\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003e1\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\u003c/table\u003e\n\u003cp\u003eand these representations for the \u003cspan\u003e“\u003cspan\u003efalse\u003c/span\u003e”\u003c/span\u003e state:\u003c/p\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003efalse\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003eno\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003eoff\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003e0\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\u003c/table\u003e\n\u003cp\u003eUnique prefixes of these strings are also accepted, for example \u003ccode\u003et\u003c/code\u003e or \u003ccode\u003en\u003c/code\u003e. Leading or trailing whitespace is ignored, and case does not matter.\u003c/p\u003e\n\u003cp\u003eThe datatype output function for type \u003ccode\u003eboolean\u003c/code\u003e always emits either \u003ccode\u003et\u003c/code\u003e or \u003ccode\u003ef\u003c/code\u003e, as shown in \u003ca href=\"/docs/18/datatype-boolean.html#DATATYPE-BOOLEAN-EXAMPLE\" rel=\"nofollow\"\u003eExample 8.2\u003c/a\u003e.\u003c/p\u003e\n\u003cdiv id=\"DATATYPE-BOOLEAN-EXAMPLE\"\u003e\n\u003cp\u003e\u003cstrong\u003eExample 8.2. Using the \u003ccode\u003eboolean\u003c/code\u003e Type\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv\u003e\n\u003cpre\u003eCREATE TABLE test1 (a boolean, b text);\nINSERT INTO test1 VALUES (TRUE, \u0026#39;sic est\u0026#39;);\nINSERT INTO test1 VALUES (FALSE, \u0026#39;non est\u0026#39;);\nSELECT * FROM test1;\n a |    b\n---+---------\n t | sic est\n f | non est\n\nSELECT * FROM test1 WHERE a;\n a |    b\n---+---------\n t | sic est\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003c/div\u003e\u003cbr\u003e\n\u003cp\u003eThe key words \u003ccode\u003eTRUE\u003c/code\u003e and \u003ccode\u003eFALSE\u003c/code\u003e are the preferred (SQL-compliant) method for writing Boolean constants in SQL queries. But you can also use the string representations by following the generic string-literal constant syntax described in \u003ca href=\"/docs/18/sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS-GENERIC\" rel=\"nofollow\"\u003eSection 4.1.2.7\u003c/a\u003e, for example \u003ccode\u003e\u0026#39;yes\u0026#39;::boolean\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003eNote that the parser automatically understands that \u003ccode\u003eTRUE\u003c/code\u003e and \u003ccode\u003eFALSE\u003c/code\u003e are of type \u003ccode\u003eboolean\u003c/code\u003e, but this is not so for \u003ccode\u003eNULL\u003c/code\u003e because that can have any type. So in some contexts you might have to cast \u003ccode\u003eNULL\u003c/code\u003e to \u003ccode\u003eboolean\u003c/code\u003e explicitly, for example \u003ccode\u003eNULL::boolean\u003c/code\u003e. Conversely, the cast can be omitted from a string-literal Boolean value in contexts where the parser can deduce that the literal must be of type \u003ccode\u003eboolean\u003c/code\u003e.\u003c/p\u003e\n\u003c/div\u003e","SourceRevision":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","ContentHash":"d45459115d35cca9d1d7f858cdbfe204e80e7950438e7d623fa223bb223bdef0","Payload":{"description":["logical Boolean (true/false)"],"manual_html":"\u003cdiv class=\"sect1\" id=\"DATATYPE-BOOLEAN\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch2 class=\"title\"\u003e8.6. Boolean Type \u003c/h2\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003e\u003cspan class=\"productname\"\u003ePostgreSQL\u003c/span\u003e provides the standard SQL type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e; see \u003ca class=\"xref\" href=\"/docs/18/datatype-boolean.html#DATATYPE-BOOLEAN-TABLE\" title=\"Table 8.19. Boolean Data Type\"\u003eTable 8.19\u003c/a\u003e. The \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e type can have several states: \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003etrue\u003c/span\u003e”\u003c/span\u003e, \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003efalse\u003c/span\u003e”\u003c/span\u003e, and a third state, \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003eunknown\u003c/span\u003e”\u003c/span\u003e, which is represented by the SQL null value.\u003c/p\u003e\n\u003cdiv class=\"table\" id=\"DATATYPE-BOOLEAN-TABLE\"\u003e\n\u003cp class=\"title\"\u003e\u003cstrong\u003eTable 8.19. Boolean Data Type\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv class=\"table-contents\"\u003e\n\u003ctable class=\"table\"\u003e\n\n\n\n\n\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eName\u003c/th\u003e\n\u003cth\u003eStorage Size\u003c/th\u003e\n\u003cth\u003eDescription\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"type\"\u003eboolean\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e1 byte\u003c/td\u003e\n\u003ctd\u003estate of true or false\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\u003cbr class=\"table-break\"\u003e\n\u003cp\u003eBoolean constants can be represented in SQL queries by the SQL key words \u003ccode class=\"literal\"\u003eTRUE\u003c/code\u003e, \u003ccode class=\"literal\"\u003eFALSE\u003c/code\u003e, and \u003ccode class=\"literal\"\u003eNULL\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003eThe datatype input function for type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e accepts these string representations for the \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003etrue\u003c/span\u003e”\u003c/span\u003e state:\u003c/p\u003e\n\u003ctable class=\"simplelist\"\u003e\n\u003ctbody\u003e\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003etrue\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003eyes\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003eon\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003e1\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\u003c/table\u003e\n\u003cp\u003eand these representations for the \u003cspan class=\"quote\"\u003e“\u003cspan class=\"quote\"\u003efalse\u003c/span\u003e”\u003c/span\u003e state:\u003c/p\u003e\n\u003ctable class=\"simplelist\"\u003e\n\u003ctbody\u003e\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003efalse\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003eno\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003eoff\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode class=\"literal\"\u003e0\u003c/code\u003e\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\u003c/table\u003e\n\u003cp\u003eUnique prefixes of these strings are also accepted, for example \u003ccode class=\"literal\"\u003et\u003c/code\u003e or \u003ccode class=\"literal\"\u003en\u003c/code\u003e. Leading or trailing whitespace is ignored, and case does not matter.\u003c/p\u003e\n\u003cp\u003eThe datatype output function for type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e always emits either \u003ccode class=\"literal\"\u003et\u003c/code\u003e or \u003ccode class=\"literal\"\u003ef\u003c/code\u003e, as shown in \u003ca class=\"xref\" href=\"/docs/18/datatype-boolean.html#DATATYPE-BOOLEAN-EXAMPLE\" title=\"Example 8.2. Using the boolean Type\"\u003eExample 8.2\u003c/a\u003e.\u003c/p\u003e\n\u003cdiv class=\"example\" id=\"DATATYPE-BOOLEAN-EXAMPLE\"\u003e\n\u003cp class=\"title\"\u003e\u003cstrong\u003eExample 8.2. Using the \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e Type\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv class=\"example-contents\"\u003e\n\u003cpre class=\"programlisting\"\u003eCREATE TABLE test1 (a boolean, b text);\nINSERT INTO test1 VALUES (TRUE, 'sic est');\nINSERT INTO test1 VALUES (FALSE, 'non est');\nSELECT * FROM test1;\n a |    b\n---+---------\n t | sic est\n f | non est\n\nSELECT * FROM test1 WHERE a;\n a |    b\n---+---------\n t | sic est\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003c/div\u003e\u003cbr class=\"example-break\"\u003e\n\u003cp\u003eThe key words \u003ccode class=\"literal\"\u003eTRUE\u003c/code\u003e and \u003ccode class=\"literal\"\u003eFALSE\u003c/code\u003e are the preferred (SQL-compliant) method for writing Boolean constants in SQL queries. But you can also use the string representations by following the generic string-literal constant syntax described in \u003ca class=\"xref\" href=\"/docs/18/sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS-GENERIC\" title=\"4.1.2.7. Constants of Other Types\"\u003eSection 4.1.2.7\u003c/a\u003e, for example \u003ccode class=\"literal\"\u003e'yes'::boolean\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003eNote that the parser automatically understands that \u003ccode class=\"literal\"\u003eTRUE\u003c/code\u003e and \u003ccode class=\"literal\"\u003eFALSE\u003c/code\u003e are of type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e, but this is not so for \u003ccode class=\"literal\"\u003eNULL\u003c/code\u003e because that can have any type. So in some contexts you might have to cast \u003ccode class=\"literal\"\u003eNULL\u003c/code\u003e to \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e explicitly, for example \u003ccode class=\"literal\"\u003eNULL::boolean\u003c/code\u003e. Conversely, the cast can be omitted from a string-literal Boolean value in contexts where the parser can deduce that the literal must be of type \u003ccode class=\"type\"\u003eboolean\u003c/code\u003e.\u003c/p\u003e\n\u003c/div\u003e","related":[{"label":"pg_type catalog","url":"/wiki/catalog/pg_type/?v=18"},{"label":"pg_cast catalog","url":"/wiki/catalog/pg_cast/?v=18"},{"label":"pg_operator catalog","url":"/wiki/catalog/pg_operator/?v=18"},{"label":"pg_opclass catalog","url":"/wiki/catalog/pg_opclass/?v=18"},{"label":"Arrays","url":"/wiki/type/arrays/?v=18"},{"label":"btree index access method","url":"/wiki/indexam/btree/?v=18"},{"label":"hash index access method","url":"/wiki/indexam/hash/?v=18"}],"sections":[]}},"RequestedLocale":"zh-Hans","Fallback":true,"Versions":["10","11","12","13","14","15","16","17","18","19","20"],"Locales":["en"],"Signatures":null,"Spellings":null,"SQLState":null,"Evidence":null}