I686LINUX/util/I686LINUX/doc/postgresql/html/tutorial-accessdb.html

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  92 ><H1
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  94 ><A
  95 NAME="TUTORIAL-ACCESSDB"
  96 >1.4. Accessing a Database</A
  97 ></H1
  98 ><A
  99 NAME="AEN478"
 100 ></A
 101 ><P
 102 >    Once you have created a database, you can access it by:
 103
 104     <P
 105 ></P
 106 ></P><UL
 107 COMPACT="COMPACT"
 108 ><LI
 109 STYLE="list-style-type: disc"
 110 ><P
 111 >       Running the <SPAN
 112 CLASS="PRODUCTNAME"
 113 >PostgreSQL</SPAN
 114 > interactive
 115        terminal program, called <SPAN
 116 CLASS="APPLICATION"
 117 ><I
 118 CLASS="FIRSTTERM"
 119 >psql</I
 120 ></SPAN
 121 >, which allows you
 122        to interactively enter, edit, and execute
 123        <ACRONYM
 124 CLASS="ACRONYM"
 125 >SQL</ACRONYM
 126 > commands.
 127       </P
 128 ></LI
 129 ><LI
 130 STYLE="list-style-type: disc"
 131 ><P
 132 >       Using an existing graphical frontend tool like
 133        <SPAN
 134 CLASS="APPLICATION"
 135 >PgAccess</SPAN
 136 > or an office suite with
 137        <ACRONYM
 138 CLASS="ACRONYM"
 139 >ODBC</ACRONYM
 140 > support to create and manipulate a
 141        database.  These possibilities are not covered in this
 142        tutorial.
 143       </P
 144 ></LI
 145 ><LI
 146 STYLE="list-style-type: disc"
 147 ><P
 148 >       Writing a custom application, using one of the several
 149        available language bindings.  These possibilities are discussed
 150        further in <A
 151 HREF="client-interfaces.html"
 152 >Part IV</A
 153 >.
 154       </P
 155 ></LI
 156 ></UL
 157 ><P>
 158
 159     You probably want to start up <TT
 160 CLASS="COMMAND"
 161 >psql</TT
 162 >, to try out
 163     the examples in this tutorial.  It can be activated for the
 164     <TT
 165 CLASS="LITERAL"
 166 >mydb</TT
 167 > database by typing the command:
 168 </P><PRE
 169 CLASS="SCREEN"
 170 ><SAMP
 171 CLASS="PROMPT"
 172 >$</SAMP
 173 > <KBD
 174 CLASS="USERINPUT"
 175 >psql mydb</KBD
 176 ></PRE
 177 ><P>
 178     If you leave off the database name then it will default to your
 179     user account name.  You already discovered this scheme in the
 180     previous section.
 181    </P
 182 ><P
 183 >    In <TT
 184 CLASS="COMMAND"
 185 >psql</TT
 186 >, you will be greeted with the following
 187     message:
 188 </P><PRE
 189 CLASS="SCREEN"
 190 >Welcome to psql 7.4.1, the PostgreSQL interactive terminal.
 191
 192 Type:  \copyright for distribution terms
 193        \h for help with SQL commands
 194        \? for help on internal slash commands
 195        \g or terminate with semicolon to execute query
 196        \q to quit
 197
 198 mydb=&gt;</PRE
 199 ><P>
 200     <A
 201 NAME="AEN503"
 202 ></A
 203 >
 204     The last line could also be
 205 </P><PRE
 206 CLASS="SCREEN"
 207 >mydb=#</PRE
 208 ><P>
 209     That would mean you are a database superuser, which is most likely
 210     the case if you installed <SPAN
 211 CLASS="PRODUCTNAME"
 212 >PostgreSQL</SPAN
 213 >
 214     yourself.  Being a superuser means that you are not subject to
 215     access controls.  For the purpose of this tutorial this is not of
 216     importance.
 217    </P
 218 ><P
 219 >    If you have encountered problems starting <TT
 220 CLASS="COMMAND"
 221 >psql</TT
 222 >
 223     then go back to the previous section.  The diagnostics of
 224     <TT
 225 CLASS="COMMAND"
 226 >psql</TT
 227 > and <TT
 228 CLASS="COMMAND"
 229 >createdb</TT
 230 > are
 231     similar, and if the latter worked the former should work as well.
 232    </P
 233 ><P
 234 >    The last line printed out by <TT
 235 CLASS="COMMAND"
 236 >psql</TT
 237 > is the
 238     prompt, and it indicates that <TT
 239 CLASS="COMMAND"
 240 >psql</TT
 241 > is listening
 242     to you and that you can type <ACRONYM
 243 CLASS="ACRONYM"
 244 >SQL</ACRONYM
 245 > queries into a
 246     work space maintained by <TT
 247 CLASS="COMMAND"
 248 >psql</TT
 249 >.  Try out these
 250     commands:
 251     <A
 252 NAME="AEN516"
 253 ></A
 254 >
 255 </P><PRE
 256 CLASS="SCREEN"
 257 ><SAMP
 258 CLASS="PROMPT"
 259 >mydb=&gt;</SAMP
 260 > <KBD
 261 CLASS="USERINPUT"
 262 >SELECT version();</KBD
 263 >
 264                             version
 265 ----------------------------------------------------------------
 266  PostgreSQL 7.4.1 on i586-pc-linux-gnu, compiled by GCC 2.96
 267 (1 row)
 268
 269 <SAMP
 270 CLASS="PROMPT"
 271 >mydb=&gt;</SAMP
 272 > <KBD
 273 CLASS="USERINPUT"
 274 >SELECT current_date;</KBD
 275 >
 276     date
 277 ------------
 278  2002-08-31
 279 (1 row)
 280
 281 <SAMP
 282 CLASS="PROMPT"
 283 >mydb=&gt;</SAMP
 284 > <KBD
 285 CLASS="USERINPUT"
 286 >SELECT 2 + 2;</KBD
 287 >
 288  ?column?
 289 ----------
 290         4
 291 (1 row)</PRE
 292 ><P>
 293    </P
 294 ><P
 295 >    The <TT
 296 CLASS="COMMAND"
 297 >psql</TT
 298 > program has a number of internal
 299     commands that are not SQL commands.  They begin with the backslash
 300     character, <SPAN
 301 CLASS="QUOTE"
 302 >"<TT
 303 CLASS="LITERAL"
 304 >\</TT
 305 >"</SPAN
 306 >.  Some of these
 307     commands were listed in the welcome message.  For example,
 308     you can get help on the syntax of various
 309     <SPAN
 310 CLASS="PRODUCTNAME"
 311 >PostgreSQL</SPAN
 312 > <ACRONYM
 313 CLASS="ACRONYM"
 314 >SQL</ACRONYM
 315 >
 316     commands by typing:
 317 </P><PRE
 318 CLASS="SCREEN"
 319 ><SAMP
 320 CLASS="PROMPT"
 321 >mydb=&gt;</SAMP
 322 > <KBD
 323 CLASS="USERINPUT"
 324 >\h</KBD
 325 ></PRE
 326 ><P>
 327    </P
 328 ><P
 329 >    To get out of <TT
 330 CLASS="COMMAND"
 331 >psql</TT
 332 >, type
 333 </P><PRE
 334 CLASS="SCREEN"
 335 ><SAMP
 336 CLASS="PROMPT"
 337 >mydb=&gt;</SAMP
 338 > <KBD
 339 CLASS="USERINPUT"
 340 >\q</KBD
 341 ></PRE
 342 ><P>
 343     and <TT
 344 CLASS="COMMAND"
 345 >psql</TT
 346 > will quit and return you to your
 347     command shell. (For more internal commands, type
 348     <TT
 349 CLASS="LITERAL"
 350 >\?</TT
 351 > at the <TT
 352 CLASS="COMMAND"
 353 >psql</TT
 354 > prompt.)  The
 355     full capabilities of <TT
 356 CLASS="COMMAND"
 357 >psql</TT
 358 > are documented in
 359     <A
 360 HREF="app-psql.html"
 361 ><SPAN
 362 CLASS="APPLICATION"
 363 >psql</SPAN
 364 ></A
 365 >.  If <SPAN
 366 CLASS="PRODUCTNAME"
 367 >PostgreSQL</SPAN
 368 > is
 369     installed correctly you can also type <TT
 370 CLASS="LITERAL"
 371 >man psql</TT
 372 >
 373     at the operating system shell prompt to see the documentation.  In
 374     this tutorial we will not use these features explicitly, but you
 375     can use them yourself when you see fit.
 376    </P
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