diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/ref/copy.sgml | 16 | ||||
| -rw-r--r-- | doc/src/sgml/ref/declare.sgml | 137 | ||||
| -rw-r--r-- | doc/src/sgml/ref/fetch.sgml | 53 | ||||
| -rw-r--r-- | doc/src/sgml/ref/move.sgml | 10 | ||||
| -rw-r--r-- | doc/src/sgml/sql.sgml | 106 |
5 files changed, 190 insertions, 132 deletions
diff --git a/doc/src/sgml/ref/copy.sgml b/doc/src/sgml/ref/copy.sgml index 8aa5b90a9ed..389b455fde7 100644 --- a/doc/src/sgml/ref/copy.sgml +++ b/doc/src/sgml/ref/copy.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.40 2002/09/21 18:32:54 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.41 2003/03/27 16:51:27 momjian Exp $ PostgreSQL documentation --> @@ -133,9 +133,10 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class=" </para> <note> <para> - On a copy in, any data item that matches this string will be stored as - a NULL value, so you should make sure that you use the same string - as you used on copy out. + On a <command>COPY FROM</command>, any data item that matches + this string will be stored as a NULL value, so you should + make sure that you use the same string as you used with + <command>COPY TO</command>. </para> </note> </listitem> @@ -210,7 +211,8 @@ ERROR: <replaceable>reason</replaceable> or write to a file. The file must be accessible to the backend and the name must be specified from the viewpoint of the backend. When <filename>stdin</filename> or <filename>stdout</filename> is - specified, data flows through the client frontend to the backend. + specified, data is transmitted via the connection between the + client frontend and the backend. <tip> <para> @@ -234,8 +236,8 @@ ERROR: <replaceable>reason</replaceable> Notes </title> <para> - <command>COPY</command> can only be used with plain tables, not with - views. + <command>COPY</command> can only be used with plain tables, not + with views. </para> <para> diff --git a/doc/src/sgml/ref/declare.sgml b/doc/src/sgml/ref/declare.sgml index 2801aeeabb2..f0673c44b67 100644 --- a/doc/src/sgml/ref/declare.sgml +++ b/doc/src/sgml/ref/declare.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/declare.sgml,v 1.20 2003/03/21 17:11:46 momjian Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/declare.sgml,v 1.21 2003/03/27 16:51:27 momjian Exp $ PostgreSQL documentation --> @@ -21,8 +21,8 @@ PostgreSQL documentation <date>1999-07-20</date> </refsynopsisdivinfo> <synopsis> -DECLARE <replaceable class="parameter">cursorname</replaceable> [ BINARY ] [ INSENSITIVE ] [ SCROLL ] - CURSOR FOR <replaceable class="parameter">query</replaceable> +DECLARE <replaceable class="parameter">cursorname</replaceable> [ BINARY ] [ INSENSITIVE ] [ [ NO ] SCROLL ] + CURSOR [ { WITH | WITHOUT } HOLD ] FOR <replaceable class="parameter">query</replaceable> [ FOR { READ ONLY | UPDATE [ OF <replaceable class="parameter">column</replaceable> [, ...] ] ] </synopsis> <refsect2 id="R2-SQL-DECLARE-1"> @@ -38,7 +38,8 @@ DECLARE <replaceable class="parameter">cursorname</replaceable> [ BINARY ] [ INS <term><replaceable class="parameter">cursorname</replaceable></term> <listitem> <para> - The name of the cursor to be used in subsequent FETCH operations. + The name of the cursor to be used in subsequent + <command>FETCH</command> operations. </para> </listitem> </varlistentry> @@ -57,8 +58,20 @@ DECLARE <replaceable class="parameter">cursorname</replaceable> [ BINARY ] [ INS <listitem> <para> <acronym>SQL92</acronym> keyword indicating that data retrieved - from the cursor should be unaffected by updates from other processes or cursors. - By default, all cursors are insensitive. This keyword has no effect. + from the cursor should be unaffected by updates from other + processes or cursors. By default, all cursors are insensitive. + This keyword currently has no effect and is present for + compatibility with the SQL standard. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>NO SCROLL</term> + <listitem> + <para> + Specifies that the cursor cannot be used to retrieve rows in a + nonsequential fashion (e.g., backward). </para> </listitem> </varlistentry> @@ -67,8 +80,33 @@ DECLARE <replaceable class="parameter">cursorname</replaceable> [ BINARY ] [ INS <term>SCROLL</term> <listitem> <para> - Specifies that the cursor may be used to retrieve rows - in a nonsequential fashion (e.g., backwards). + Specifies that the cursor may be used to retrieve rows in a + nonsequential fashion (e.g., backward). Depending upon the + complexity of the query's execution plan, specifying + <literal>SCROLL</literal> may impose a slight performance penalty + on the query's execution time. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>WITHOUT HOLD</term> + <listitem> + <para> + Specifies that the cursor cannot be used outside of the + transaction that created it. If neither <literal>WITHOUT + HOLD</literal> nor <literal>WITH HOLD</literal> is specified, + <literal>WITH HOLD</literal> is the default. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>WITH HOLD</term> + <listitem> + <para> + Specifies that the cursor may be used after the transaction + that creates it successfully commits. </para> </listitem> </varlistentry> @@ -124,7 +162,8 @@ DECLARE <replaceable class="parameter">cursorname</replaceable> [ BINARY ] [ INS </para> <para> - The BINARY, INSENSITIVE, and SCROLL keywords may appear in any order. + The <literal>BINARY</literal>, <literal>INSENSITIVE</literal>, + <literal>SCROLL</literal> keywords may appear in any order. </para> </refsect2> @@ -144,7 +183,7 @@ DECLARE CURSOR </computeroutput></term> <listitem> <para> - The message returned if the SELECT is run successfully. + The message returned if the <command>SELECT</command> is run successfully. </para> </listitem> </varlistentry> @@ -155,9 +194,8 @@ WARNING: Closing pre-existing portal "<replaceable class="parameter">cursorname </computeroutput></term> <listitem> <para> - This message is reported if the same cursor name was already declared - in the current transaction block. The previous definition is - discarded. + This message is reported if a cursor with the same name already + exists. The previous definition is discarded. </para> </listitem> </varlistentry> @@ -168,7 +206,9 @@ ERROR: DECLARE CURSOR may only be used in begin/end transaction blocks </computeroutput></term> <listitem> <para> - This error occurs if the cursor is not declared within a transaction block. + This error occurs if the cursor is not declared within a + transaction block, and <literal>WITH HOLD</literal> is not + specified. </para> </listitem> </varlistentry> @@ -193,16 +233,14 @@ ERROR: DECLARE CURSOR may only be used in begin/end transaction blocks </para> <para> - Normal cursors return data in text format, the same as a <command>SELECT</> - would produce. Since - data is stored natively in binary format, the system must - do a conversion to produce the text format. In addition, - text formats are often larger in size than the corresponding binary format. - Once the information comes back in text form, the client - application may need to convert it to a binary format to - manipulate it. - BINARY cursors give you back the data in the native binary - representation. + Normal cursors return data in text format, the same as a + <command>SELECT</> would produce. Since data is stored natively in + binary format, the system must do a conversion to produce the text + format. In addition, text formats are often larger in size than the + corresponding binary format. Once the information comes back in + text form, the client application may need to convert it to a + binary format to manipulate it. BINARY cursors give you back the + data in the native binary representation. </para> <para> @@ -245,7 +283,9 @@ ERROR: DECLARE CURSOR may only be used in begin/end transaction blocks </title> <para> - Cursors are only available within transactions. Use + If <literal>WITH HOLD</literal> is not specified, the cursor + created by this command can only be used within the current + transaction. Use <xref linkend="sql-begin" endterm="sql-begin-title">, <xref linkend="sql-commit" endterm="sql-commit-title"> and @@ -254,12 +294,25 @@ ERROR: DECLARE CURSOR may only be used in begin/end transaction blocks </para> <para> - The <literal>SCROLL</> option should be specified when defining a cursor - that will be used to fetch backwards. This is required by - <acronym>SQL92</acronym>. However, for compatibility with - earlier versions, <productname>PostgreSQL</productname> will allow - backward fetches without <literal>SCROLL</>, if the cursor's query plan - is simple enough that no extra overhead is needed to support it. + If <literal>WITH HOLD</literal> is specified and the transaction + that created the cursor successfully commits, the cursor can be + accessed outside the creating transaction. If the creating + transaction is aborted, the cursor is removed. A cursor created + with <literal>WITH HOLD</literal> is closed when an explicit + <command>CLOSE</command> command is issued on it, or the client + connection is terminated. + </para> + + <para> + The <literal>SCROLL</> option should be specified when defining a + cursor that will be used to fetch backwards. This is required by + <acronym>SQL92</acronym>. However, for compatibility with earlier + versions, <productname>PostgreSQL</productname> will allow + backward fetches without <literal>SCROLL</>, if the cursor's query + plan is simple enough that no extra overhead is needed to support + it. However, application developers are advised not to rely on + using backward fetches from a cursor that has not been created + with <literal>SCROLL</literal>. </para> <para> @@ -271,7 +324,7 @@ ERROR: DECLARE CURSOR may only be used in begin/end transaction blocks However, <application>ecpg</application>, the embedded SQL preprocessor for <productname>PostgreSQL</productname>, supports the <acronym>SQL92</acronym> cursor conventions, including those - involving DECLARE and OPEN statements. + involving <command>DECLARE</command> and <command>OPEN</command> statements. </para> </refsect2> </refsect1> @@ -303,13 +356,21 @@ DECLARE liahona CURSOR SQL92 </title> <para> - <acronym>SQL92</acronym> allows cursors only in embedded <acronym>SQL</acronym> - and in modules. <productname>PostgreSQL</productname> permits cursors to be used - interactively. + <para> + <acronym>SQL92</acronym> allows cursors only in embedded + <acronym>SQL</acronym> and in modules. <productname>PostgreSQL</> + permits cursors to be used interactively. + </para> + + <para> <acronym>SQL92</acronym> allows embedded or modular cursors to - update database information. - All <productname>PostgreSQL</productname> cursors are read only. - The BINARY keyword is a <productname>PostgreSQL</productname> extension. + update database information. All <productname>PostgreSQL</> + cursors are read only. + </para> + + <para> + The <literal>BINARY</literal> keyword is a + <productname>PostgreSQL</productname> extension. </para> </refsect2> </refsect1> diff --git a/doc/src/sgml/ref/fetch.sgml b/doc/src/sgml/ref/fetch.sgml index 8f3244eb39f..a1f3b13719f 100644 --- a/doc/src/sgml/ref/fetch.sgml +++ b/doc/src/sgml/ref/fetch.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/fetch.sgml,v 1.27 2003/03/11 19:40:22 tgl Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/fetch.sgml,v 1.28 2003/03/27 16:51:27 momjian Exp $ PostgreSQL documentation --> @@ -251,8 +251,7 @@ WARNING: PerformPortalFetch: portal "<replaceable class="PARAMETER">cursor</rep </computeroutput></term> <listitem> <para> - If <replaceable class="PARAMETER">cursor</replaceable> is not known. - The cursor must have been declared within the current transaction block. + There is no cursor with the specified name. </para> </listitem> </varlistentry> @@ -326,7 +325,9 @@ WARNING: PerformPortalFetch: portal "<replaceable class="PARAMETER">cursor</rep use any variants of <command>FETCH</> other than <command>FETCH NEXT</> or <command>FETCH FORWARD</> with a positive count. For simple queries <productname>PostgreSQL</productname> will allow backwards fetch from - cursors not declared with SCROLL, but this behavior is best not relied on. + cursors not declared with SCROLL, but this behavior is best not + relied on. If the cursor is declared with NO SCROLL, no backward + fetches are allowed. </para> <para> @@ -339,16 +340,11 @@ WARNING: PerformPortalFetch: portal "<replaceable class="PARAMETER">cursor</rep </para> <para> - Updating data via a cursor is not supported by - <productname>PostgreSQL</productname>, - because mapping cursor updates back to base tables is - not generally possible, as is also the case with VIEW updates. - Consequently, - users must issue explicit UPDATE commands to replace data. - </para> - - <para> - Cursors may only be used inside transaction blocks. + Updating data via a cursor is not supported by + <productname>PostgreSQL</productname>, because mapping cursor + updates back to base tables is not generally possible, as is also + the case with view updates. Consequently, users must issue + explicit <command>UPDATE</command> commands to replace data. </para> <para> @@ -357,12 +353,6 @@ WARNING: PerformPortalFetch: portal "<replaceable class="PARAMETER">cursor</rep Use <xref linkend="sql-move" endterm="sql-move-title"> to change cursor position without retrieving data. - Refer to - <xref linkend="sql-begin" endterm="sql-begin-title">, - <xref linkend="sql-commit" endterm="sql-commit-title">, - and - <xref linkend="sql-rollback" endterm="sql-rollback-title"> - for further information about transactions. </para> </refsect2> </refsect1> @@ -379,7 +369,7 @@ WARNING: PerformPortalFetch: portal "<replaceable class="PARAMETER">cursor</rep -- Set up and use a cursor: BEGIN WORK; -DECLARE liahona CURSOR FOR SELECT * FROM films; +DECLARE liahona SCROLL CURSOR FOR SELECT * FROM films; -- Fetch first 5 rows in the cursor liahona: FETCH FORWARD 5 IN liahona; @@ -425,9 +415,10 @@ COMMIT WORK; </title> <para> - <acronym>SQL92</acronym> defines FETCH for use in embedded contexts only. - Therefore, it describes placing the results into explicit variables using - an <literal>INTO</> clause, for example: + <acronym>SQL92</acronym> defines <command>FETCH</command> for use + in embedded contexts only. Therefore, it describes placing the + results into explicit variables using an <literal>INTO</> clause, + for example: <synopsis> FETCH ABSOLUTE <replaceable class="PARAMETER">n</replaceable> @@ -435,16 +426,18 @@ FETCH ABSOLUTE <replaceable class="PARAMETER">n</replaceable> INTO :<replaceable class="PARAMETER">variable</replaceable> [, ...] </synopsis> - <productname>PostgreSQL</productname>'s use of non-embedded cursors - is non-standard, and so is its practice of returning the result data - as if it were a SELECT result. Other than this point, FETCH is fully + <productname>PostgreSQL</productname>'s use of non-embedded + cursors is non-standard, and so is its practice of returning the + result data as if it were a <command>SELECT</command> result. + Other than this point, <command>FETCH</command> is fully upward-compatible with <acronym>SQL92</acronym>. </para> <para> - The FETCH forms involving FORWARD and BACKWARD (including the forms - FETCH <replaceable class="PARAMETER">count</replaceable> and FETCH ALL, - in which FORWARD is implicit) are <productname>PostgreSQL</productname> + The <command>FETCH</command> forms involving FORWARD and BACKWARD + (including the forms FETCH <replaceable + class="PARAMETER">count</replaceable> and FETCH ALL, in which + FORWARD is implicit) are <productname>PostgreSQL</productname> extensions. </para> diff --git a/doc/src/sgml/ref/move.sgml b/doc/src/sgml/ref/move.sgml index f01ee9d8a58..cd6d6aca0fd 100644 --- a/doc/src/sgml/ref/move.sgml +++ b/doc/src/sgml/ref/move.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/move.sgml,v 1.20 2003/03/11 19:40:22 tgl Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/move.sgml,v 1.21 2003/03/27 16:51:27 momjian Exp $ PostgreSQL documentation --> @@ -64,12 +64,6 @@ MOVE [ <replaceable class="PARAMETER">direction</replaceable> { FROM | IN } ] <r Refer to <xref linkend="sql-declare" endterm="sql-declare-title"> to define a cursor. - Refer to - <xref linkend="sql-begin" endterm="sql-begin-title">, - <xref linkend="sql-commit" endterm="sql-commit-title">, - and - <xref linkend="sql-rollback" endterm="sql-rollback-title"> - for further information about transactions. </para> </refsect2> </refsect1> @@ -83,7 +77,7 @@ MOVE [ <replaceable class="PARAMETER">direction</replaceable> { FROM | IN } ] <r <programlisting> BEGIN WORK; -DECLARE liahona CURSOR FOR SELECT * FROM films; +DECLARE liahona CURSOR FOR SELECT * FROM films; -- Skip first 5 rows: MOVE FORWARD 5 IN liahona; <computeroutput> diff --git a/doc/src/sgml/sql.sgml b/doc/src/sgml/sql.sgml index 9e788ff0616..89de6668028 100644 --- a/doc/src/sgml/sql.sgml +++ b/doc/src/sgml/sql.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/sql.sgml,v 1.29 2003/02/19 04:06:28 momjian Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/sql.sgml,v 1.30 2003/03/27 16:51:26 momjian Exp $ --> <chapter id="sql"> @@ -851,7 +851,7 @@ A < B + 3. <para> The most often used command in <acronym>SQL</acronym> is the - SELECT statement, + <command>SELECT</command> statement, used to retrieve data. The syntax is: <synopsis> @@ -881,7 +881,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="PARAMETER">expression</replac <title>Simple Selects</title> <para> - Here are some simple examples using a SELECT statement: + Here are some simple examples using a <command>SELECT</command> statement: <example> <title id="simple-query">Simple Query with Qualification</title> @@ -905,9 +905,10 @@ SELECT * FROM PART </para> <para> - Using <quote>*</quote> in the SELECT statement will deliver all attributes from - the table. If we want to retrieve only the attributes PNAME and PRICE - from table PART we use the statement: + Using <quote>*</quote> in the <command>SELECT</command> statement + will deliver all attributes from the table. If we want to retrieve + only the attributes PNAME and PRICE from table PART we use the + statement: <programlisting> SELECT PNAME, PRICE @@ -924,9 +925,9 @@ SELECT PNAME, PRICE Cam | 25 </programlisting> - Note that the <acronym>SQL</acronym> SELECT corresponds to the - <quote>projection</quote> in relational algebra not to the - <quote>selection</quote> (see <xref linkend="rel-alg" + Note that the <acronym>SQL</acronym> <command>SELECT</command> + corresponds to the <quote>projection</quote> in relational algebra + not to the <quote>selection</quote> (see <xref linkend="rel-alg" endterm="rel-alg"> for more details). </para> @@ -1252,15 +1253,15 @@ select sname, pname from supplier <title id="aggregates-tutorial">Aggregate Operators</title> <para> - <acronym>SQL</acronym> provides aggregate operators - (e.g. AVG, COUNT, SUM, MIN, MAX) that - take an expression as argument. The expression is evaluated at - each row that satisfies the WHERE clause, and the aggregate operator - is calculated over this set of input values. Normally, an aggregate - delivers a single result for a whole SELECT statement. But if - grouping is specified in the query, then a separate calculation is done - over the rows of each group, and an aggregate result is delivered per - group (see next section). + <acronym>SQL</acronym> provides aggregate operators (e.g. AVG, + COUNT, SUM, MIN, MAX) that take an expression as argument. The + expression is evaluated at each row that satisfies the WHERE + clause, and the aggregate operator is calculated over this set + of input values. Normally, an aggregate delivers a single + result for a whole <command>SELECT</command> statement. But if + grouping is specified in the query, then a separate calculation + is done over the rows of each group, and an aggregate result is + delivered per group (see next section). <example> <title id="aggregates-example">Aggregates</title> @@ -1413,11 +1414,12 @@ SELECT S.SNO, S.SNAME, COUNT(SE.PNO) </para> <para> - Also observe that it makes no sense to ask for an aggregate of an - aggregate, e.g., AVG(MAX(sno)), because a SELECT only does one pass - of grouping and aggregation. You can get a result of this kind by - using a temporary table or a sub-SELECT in the FROM clause to - do the first level of aggregation. + Also observe that it makes no sense to ask for an aggregate of + an aggregate, e.g., AVG(MAX(sno)), because a + <command>SELECT</command> only does one pass of grouping and + aggregation. You can get a result of this kind by using a + temporary table or a sub-SELECT in the FROM clause to do the + first level of aggregation. </para> </sect3> @@ -1502,16 +1504,18 @@ SELECT * </para> <para> - When we look at the above query we can see - the keyword SELECT two times. The first one at the beginning of the - query - we will refer to it as outer SELECT - and the one in the WHERE - clause which begins a nested query - we will refer to it as inner - SELECT. For every tuple of the outer SELECT the inner SELECT has to be - evaluated. After every evaluation we know the price of the tuple named - 'Screw' and we can check if the price of the actual tuple is - greater. (Actually, in this example the inner query need only be - evaluated once, since it does not depend on the state of the outer - query.) + When we look at the above query we can see the keyword + <command>SELECT</command> two times. The first one at the + beginning of the query - we will refer to it as outer + <command>SELECT</command> - and the one in the WHERE clause which + begins a nested query - we will refer to it as inner + <command>SELECT</command>. For every tuple of the outer + <command>SELECT</command> the inner <command>SELECT</command> has + to be evaluated. After every evaluation we know the price of the + tuple named 'Screw' and we can check if the price of the actual + tuple is greater. (Actually, in this example the inner query need + only be evaluated once, since it does not depend on the state of + the outer query.) </para> <para> @@ -1528,11 +1532,13 @@ SELECT * </para> <para> - In our example the result will be empty because every supplier sells - at least one part. Note that we use S.SNO from the outer SELECT within - the WHERE clause of the inner SELECT. Here the subquery must be - evaluated afresh for each tuple from the outer query, i.e. the value for - S.SNO is always taken from the current tuple of the outer SELECT. + In our example the result will be empty because every supplier + sells at least one part. Note that we use S.SNO from the outer + <command>SELECT</command> within the WHERE clause of the inner + <command>SELECT</command>. Here the subquery must be evaluated + afresh for each tuple from the outer query, i.e. the value for + S.SNO is always taken from the current tuple of the outer + <command>SELECT</command>. </para> </example> </para> @@ -1670,7 +1676,7 @@ EXCEPT <para> The most fundamental command for data definition is the one that creates a new relation (a new table). The syntax of the - CREATE TABLE command is: + <command>CREATE TABLE</command> command is: <synopsis> CREATE TABLE <replaceable class="parameter">table_name</replaceable> @@ -1786,7 +1792,7 @@ CREATE TABLE SELLS <para> To create an index in <acronym>SQL</acronym> - the CREATE INDEX command is used. The syntax is: + the <command>CREATE INDEX</command> command is used. The syntax is: <programlisting> CREATE INDEX <replaceable class="parameter">index_name</replaceable> @@ -1808,10 +1814,11 @@ CREATE INDEX I ON SUPPLIER (SNAME); </para> <para> - The created index is maintained automatically, i.e. whenever a new tuple - is inserted into the relation SUPPLIER the index I is adapted. Note - that the only changes a user can perceive when an index is present - are increased speed for SELECT and decreases in speed of updates. + The created index is maintained automatically, i.e. whenever a new + tuple is inserted into the relation SUPPLIER the index I is + adapted. Note that the only changes a user can perceive when an + index is present are increased speed for <command>SELECT</command> + and decreases in speed of updates. </para> </example> </para> @@ -1916,7 +1923,7 @@ SELECT * FROM London_Suppliers <para> To destroy a table (including all tuples stored in that table) the - DROP TABLE command is used: + <command>DROP TABLE</command> command is used: <programlisting> DROP TABLE <replaceable class="parameter">table_name</replaceable>; @@ -1932,7 +1939,7 @@ DROP TABLE SUPPLIER; </para> <para> - The DROP INDEX command is used to destroy an index: + The <command>DROP INDEX</command> command is used to destroy an index: <programlisting> DROP INDEX <replaceable class="parameter">index_name</replaceable>; @@ -1940,7 +1947,8 @@ DROP INDEX <replaceable class="parameter">index_name</replaceable>; </para> <para> - Finally to destroy a given view use the command DROP VIEW: + Finally to destroy a given view use the command <command>DROP + VIEW</command>: <programlisting> DROP VIEW <replaceable class="parameter">view_name</replaceable>; @@ -1994,7 +2002,7 @@ INSERT INTO SELLS (SNO, PNO) <para> To change one or more attribute values of tuples in a relation the - UPDATE command is used. The syntax is: + <command>UPDATE</command> command is used. The syntax is: <programlisting> UPDATE <replaceable class="parameter">table_name</replaceable> @@ -2126,7 +2134,7 @@ DELETE FROM SUPPLIER need a mechanism to access every single tuple of the set of tuples returned by a SELECT statement. This mechanism can be provided by declaring a <firstterm>cursor</firstterm>. - After that we can use the FETCH command to + After that we can use the <command>FETCH</command> command to retrieve a tuple and set the cursor to the next tuple. </para> |