<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Boolean Type</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 8.0.11 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Data Types" HREF="datatype.html"><LINK REL="PREVIOUS" TITLE="Date/Time Types" HREF="datatype-datetime.html"><LINK REL="NEXT" TITLE="Geometric Types" HREF="datatype-geometric.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2007-02-02T03:57:22"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" >PostgreSQL 8.0.11 Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="datatype-datetime.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="datatype.html" >Fast Backward</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 8. Data Types</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="top" ><A HREF="datatype.html" >Fast Forward</A ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="top" ><A HREF="datatype-geometric.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="DATATYPE-BOOLEAN" >8.6. Boolean Type</A ></H1 ><A NAME="AEN4852" ></A ><A NAME="AEN4855" ></A ><A NAME="AEN4857" ></A ><P > <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > provides the standard <ACRONYM CLASS="ACRONYM" >SQL</ACRONYM > type <TT CLASS="TYPE" >boolean</TT >. <TT CLASS="TYPE" >boolean</TT > can have one of only two states: <SPAN CLASS="QUOTE" >"true"</SPAN > or <SPAN CLASS="QUOTE" >"false"</SPAN >. A third state, <SPAN CLASS="QUOTE" >"unknown"</SPAN >, is represented by the <ACRONYM CLASS="ACRONYM" >SQL</ACRONYM > null value. </P ><P > Valid literal values for the <SPAN CLASS="QUOTE" >"true"</SPAN > state are: <P ></P ><TABLE BORDER="0" ><TBODY ><TR ><TD ><TT CLASS="LITERAL" >TRUE</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'t'</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'true'</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'y'</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'yes'</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'1'</TT ></TD ></TR ></TBODY ></TABLE ><P ></P > For the <SPAN CLASS="QUOTE" >"false"</SPAN > state, the following values can be used: <P ></P ><TABLE BORDER="0" ><TBODY ><TR ><TD ><TT CLASS="LITERAL" >FALSE</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'f'</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'false'</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'n'</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'no'</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >'0'</TT ></TD ></TR ></TBODY ></TABLE ><P ></P > Using the key words <TT CLASS="LITERAL" >TRUE</TT > and <TT CLASS="LITERAL" >FALSE</TT > is preferred (and <ACRONYM CLASS="ACRONYM" >SQL</ACRONYM >-compliant). </P ><DIV CLASS="EXAMPLE" ><A NAME="DATATYPE-BOOLEAN-EXAMPLE" ></A ><P ><B >Example 8-2. Using the <TT CLASS="TYPE" >boolean</TT > type</B ></P ><PRE CLASS="PROGRAMLISTING" >CREATE TABLE test1 (a boolean, b text); INSERT INTO test1 VALUES (TRUE, 'sic est'); INSERT INTO test1 VALUES (FALSE, 'non est'); SELECT * FROM test1; a | b ---+--------- t | sic est f | non est SELECT * FROM test1 WHERE a; a | b ---+--------- t | sic est</PRE ></DIV ><P > <A HREF="datatype-boolean.html#DATATYPE-BOOLEAN-EXAMPLE" >Example 8-2</A > shows that <TT CLASS="TYPE" >boolean</TT > values are output using the letters <TT CLASS="LITERAL" >t</TT > and <TT CLASS="LITERAL" >f</TT >. </P ><DIV CLASS="TIP" ><BLOCKQUOTE CLASS="TIP" ><P ><B >Tip: </B > Values of the <TT CLASS="TYPE" >boolean</TT > type cannot be cast directly to other types (e.g., <TT CLASS="LITERAL" >CAST (<TT CLASS="REPLACEABLE" ><I >boolval</I ></TT > AS integer)</TT > does not work). This can be accomplished using the <TT CLASS="LITERAL" >CASE</TT > expression: <TT CLASS="LITERAL" >CASE WHEN <TT CLASS="REPLACEABLE" ><I >boolval</I ></TT > THEN 'value if true' ELSE 'value if false' END</TT >. See <A HREF="functions-conditional.html" >Section 9.13</A >. </P ></BLOCKQUOTE ></DIV ><P > <TT CLASS="TYPE" >boolean</TT > uses 1 byte of storage. </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="datatype-datetime.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="datatype-geometric.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Date/Time Types</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="datatype.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Geometric Types</TD ></TR ></TABLE ></DIV ></BODY ></HTML >