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<HTML
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>String Functions</TITLE
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><H1
CLASS="SECT1"
><A
NAME="AEN2021"
>String Functions</A
></H1
><P
>SQL92 defines string functions with specific syntax. Some of these
are implemented using other <SPAN
CLASS="PRODUCTNAME"
>Postgres</SPAN
> functions.</P
><P
><DIV
CLASS="TABLE"
><P
><B
>Table 7-2. <SPAN
CLASS="ACRONYM"
>SQL92</SPAN
> String Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><TR
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Function</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Returns</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Description</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Example</TH
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> position(text in text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> int4 </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> location of specified substring </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> position('o' in 'Tom') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> substring(text [from int] [for int]) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> extract specified substring </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> substring('Tom' from 2 for 2) </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> trim([leading|trailing|both] [text] from text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> trim characters from text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> trim(both 'x' from 'xTomx') </TD
></TR
></TABLE
></DIV
></P
><P
>Many string functions are available for text, varchar(), and char() types.
Some are used internally to implement the SQL92 string functions listed above.</P
><P
><DIV
CLASS="TABLE"
><P
><B
>Table 7-3. String Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><TR
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Function</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Returns</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Description</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Example</TH
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> char(text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> char </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert text to char type </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> char('text string') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> char(varchar) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> char </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert varchar to char type </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> char(varchar 'varchar string') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> initcap(text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> first letter of each word to upper case </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> initcap('thomas') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> lower(text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert text to lower case </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> lower('TOM') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> lpad(text,int,text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> left pad string to specified length </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> lpad('hi',4,'??') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> ltrim(text,text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> left trim characters from text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> ltrim('xxxxtrim','x') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> position(text,text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> extract specified substring </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> position('high','ig') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> rpad(text,int,text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> right pad string to specified length </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> rpad('hi',4,'x') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> rtrim(text,text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> right trim characters from text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> rtrim('trimxxxx','x') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> substr(text,int[,int]) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> extract specified substring </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> substr('hi there',3,5) </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text(char) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert char to text type </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text('char string') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text(varchar) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert varchar to text type </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text(varchar 'varchar string') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> translate(text,from,to) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert character in string </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> translate('12345', '1', 'a') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> varchar(char) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> varchar </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert char to varchar type </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> varchar('char string') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> varchar(text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> varchar </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert text to varchar type </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> varchar('text string') </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
> upper(text) </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> text </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> convert text to upper case </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
> upper('tom') </TD
></TR
></TABLE
></DIV
></P
><P
>Most functions explicitly defined for text will work for char() and varchar() arguments.</P
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