/ Check-in [d1d8642b]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:In the "lang.html" documentation file, put the CREATE TRIGGER and DROP TRIGGER sections in alphabetical order. (CVS 564)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1:d1d8642b57bd0765ade730248012d58b0859c12c
User & Date: drh 2002-05-15 11:43:16
Context
2002-05-15
11:44
Remove all tabs from the beginning of source code lines. Replace tabs with the appropriate number of spaces. (CVS 565) check-in: 690f9a16 user: drh tags: trunk
11:43
In the "lang.html" documentation file, put the CREATE TRIGGER and DROP TRIGGER sections in alphabetical order. (CVS 564) check-in: d1d8642b user: drh tags: trunk
08:43
Add the Makefile.in that was forgotten with checkin #562 (CVS 563) check-in: 29b8330c user: danielk1977 tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to www/lang.tcl.

1
2
3
4
5
6
7
8
9
10
11
...
341
342
343
344
345
346
347
















































































































348
349
350
351
352
353
354
...
393
394
395
396
397
398
399









400
401
402
403
404
405
406
....
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: lang.tcl,v 1.34 2002/05/15 08:30:15 danielk1977 Exp $}

puts {<html>
<head>
  <title>Query Language Understood By SQLite</title>
</head>
<body bgcolor=white>
<h1 align=center>
................................................................................
are read from the <b>sqlite_master</b> table and used to regenerate
SQLite's internal representation of the table layout.
If the original command was a CREATE TABLE AS then then an equivalent
CREATE TABLE statement is synthesized and store in <b>sqlite_master</b>
in place of the original command.
</p>
}

















































































































Section {CREATE VIEW} {createview}

Syntax {sql-command} {
CREATE VIEW <view-name> AS <select-statement>
}

................................................................................
}

Section {DROP TABLE} droptable

Syntax {sql-command} {
DROP TABLE <table-name>
}










puts {
<p>The DROP TABLE statement consists of the keywords "DROP TABLE" followed
by the name of the table.  The table named is completely removed from
the disk.  The table can not be recovered.  All indices associated with
the table are also deleted.</p>}

................................................................................
In version 1.0 of SQLite, the VACUUM command would invoke 
<b>gdbm_reorganize()</b> to clean up the backend database file.
Beginning with version 2.0 of SQLite, GDBM is no longer used for
the database backend and VACUUM has become a no-op.
</p>
}

Section {CREATE TRIGGER} createtrigger

Syntax {sql-statement} {
CREATE TRIGGER <trigger-name> [ BEFORE | AFTER ]
<database-event>
<trigger-action>
}

Syntax {database-event} {
DELETE | 
INSERT | 
UPDATE | 
UPDATE OF <column-list>
ON <table-name> 
}

Syntax {trigger-action} {
[ FOR EACH ROW ] [ WHEN <expression> ] 
BEGIN 
  <trigger-step> ; [ <trigger-step> ; ]*
END
}

Syntax {trigger-step} {
<update-statement> | <insert-statement> | 
<delete-statement> | <select-statement> 
}

puts {
<p>The CREATE TRIGGER statement is used to add triggers to the 
database schema. Triggers are database operations (the <i>trigger-action</i>) 
that are automatically performed when a specified database event (the
<i>database-event</i>) occurs.  </p>

<p>A trigger may be specified to fire whenever a DELETE, INSERT or UPDATE of a
particular database table occurs, or whenever an UPDATE of one or more
specified columns of a table are updated.</p>

<p>At this time SQLite supports only FOR EACH ROW triggers, not FOR EACH
STATEMENT triggers. Hence explicitly specifying FOR EACH ROW is optional.  FOR
EACH ROW implies that the SQL statements specified as <i>trigger-steps</i> 
may be executed (depending on the WHEN clause) for each database row being
inserted, updated or deleted by the statement causing the trigger to fire.</p>

<p>Both the WHEN clause and the <i>trigger-steps</i> may access elements of 
the row being inserted, deleted or updated using references of the form 
"NEW.<i>column-name</i>" and "OLD.<i>column-name</i>", where
<i>column-name</i> is the name of a column from the table that the trigger
is associated with. OLD and NEW references may only be used in triggers on
<i>trigger-event</i>s for which they are relevant, as follows:</p>

<table border=0 cellpadding=10>
<tr>
<td valign="top" align="right" width=120><i>INSERT</i></td>
<td valign="top">NEW references are valid</td>
</tr>
<tr>
<td valign="top" align="right" width=120><i>UPDATE</i></td>
<td valign="top">NEW and OLD references are valid</td>
</tr>
<tr>
<td valign="top" align="right" width=120><i>DELETE</i></td>
<td valign="top">OLD references are valid</td>
</tr>
</table>
</p>

<p>If a WHEN clause is supplied, the SQL statements specified as <i>trigger-steps</i> are only executed for rows for which the WHEN clause is true. If no WHEN clause is supplied, the SQL statements are executed for all rows.</p>

<p>The specified <i>trigger-time</i> determines when the <i>trigger-steps</i>
will be executed relative to the insertion, modification or removal of the
associated row.</p>

<p>An ON CONFLICT clause may be specified as part of an UPDATE or INSERT
<i>trigger-step</i>. However if an ON CONFLICT clause is specified as part of 
the statement causing the trigger to fire, then this conflict handling
policy is used instead.</p>

<p>Triggers are automatically dropped when the table that they are 
associated with is dropped.</p>

<p>Triggers may be created on views, as well as ordinary tables. If one or
more INSERT, DELETE or UPDATE triggers are defined on a view, then it is not
an error to execute an INSERT, DELETE or UPDATE statement on the view, 
respectively. Thereafter, executing an INSERT, DELETE or UPDATE on the view
causes the associated triggers to fire. The real tables underlying the view
are not modified (except possibly explicitly, by a trigger program).</p>

<p><b>Example:</b></p>

<p>Assuming that customer records are stored in the "customers" table, and
that order records are stored in the "orders" table, the following trigger
ensures that all associated orders are redirected when a customer changes
his or her address:</p>
}
Example {
CREATE TRIGGER update_customer_address UPDATE OF address ON customers 
  BEGIN
    UPDATE orders SET address = new.address WHERE customer_name = old.name;
  END;
}
puts {
<p>With this trigger installed, executing the statement:</p>
}
Example {
UPDATE customers SET address = '1 Main St.' WHERE name = 'Jack Jones';
}
puts {
<p>causes the following to be automatically executed:</p>
}
Example {
UPDATE orders SET address = '1 Main St.' WHERE customer_name = 'Jack Jones';
}

Section {DROP TRIGGER} droptrigger
Syntax {sql-statement} {
DROP TRIGGER <trigger-name>
}
puts { 
  <p>Used to drop a trigger from the database schema. Note that triggers
  are automatically dropped when the associated table is dropped.</p>
}


puts {
<p><hr /></p>
<p><a href="index.html"><img src="/goback.jpg" border=0 />
Back to the SQLite Home Page</a>
</p>

</body></html>}



|







 







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>







 







>
>
>
>
>
>
>
>
>







 







<

<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<

<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<






1
2
3
4
5
6
7
8
9
10
11
...
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
...
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
....
1208
1209
1210
1211
1212
1213
1214

1215


























1216
































































































1217
1218
1219
1220
1221
1222
#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: lang.tcl,v 1.35 2002/05/15 11:43:16 drh Exp $}

puts {<html>
<head>
  <title>Query Language Understood By SQLite</title>
</head>
<body bgcolor=white>
<h1 align=center>
................................................................................
are read from the <b>sqlite_master</b> table and used to regenerate
SQLite's internal representation of the table layout.
If the original command was a CREATE TABLE AS then then an equivalent
CREATE TABLE statement is synthesized and store in <b>sqlite_master</b>
in place of the original command.
</p>
}
Section {CREATE TRIGGER} createtrigger

Syntax {sql-statement} {
CREATE TRIGGER <trigger-name> [ BEFORE | AFTER ]
<database-event> ON <table-name>
<trigger-action>
}

Syntax {database-event} {
DELETE | 
INSERT | 
UPDATE | 
UPDATE OF <column-list>
}

Syntax {trigger-action} {
[ FOR EACH ROW ] [ WHEN <expression> ] 
BEGIN 
  <trigger-step> ; [ <trigger-step> ; ]*
END
}

Syntax {trigger-step} {
<update-statement> | <insert-statement> | 
<delete-statement> | <select-statement> 
}

puts {
<p>The CREATE TRIGGER statement is used to add triggers to the 
database schema. Triggers are database operations (the <i>trigger-action</i>) 
that are automatically performed when a specified database event (the
<i>database-event</i>) occurs.  </p>

<p>A trigger may be specified to fire whenever a DELETE, INSERT or UPDATE of a
particular database table occurs, or whenever an UPDATE of one or more
specified columns of a table are updated.</p>

<p>At this time SQLite supports only FOR EACH ROW triggers, not FOR EACH
STATEMENT triggers. Hence explicitly specifying FOR EACH ROW is optional.  FOR
EACH ROW implies that the SQL statements specified as <i>trigger-steps</i> 
may be executed (depending on the WHEN clause) for each database row being
inserted, updated or deleted by the statement causing the trigger to fire.</p>

<p>Both the WHEN clause and the <i>trigger-steps</i> may access elements of 
the row being inserted, deleted or updated using references of the form 
"NEW.<i>column-name</i>" and "OLD.<i>column-name</i>", where
<i>column-name</i> is the name of a column from the table that the trigger
is associated with. OLD and NEW references may only be used in triggers on
<i>trigger-event</i>s for which they are relevant, as follows:</p>

<table border=0 cellpadding=10>
<tr>
<td valign="top" align="right" width=120><i>INSERT</i></td>
<td valign="top">NEW references are valid</td>
</tr>
<tr>
<td valign="top" align="right" width=120><i>UPDATE</i></td>
<td valign="top">NEW and OLD references are valid</td>
</tr>
<tr>
<td valign="top" align="right" width=120><i>DELETE</i></td>
<td valign="top">OLD references are valid</td>
</tr>
</table>
</p>

<p>If a WHEN clause is supplied, the SQL statements specified as <i>trigger-steps</i> are only executed for rows for which the WHEN clause is true. If no WHEN clause is supplied, the SQL statements are executed for all rows.</p>

<p>The specified <i>trigger-time</i> determines when the <i>trigger-steps</i>
will be executed relative to the insertion, modification or removal of the
associated row.</p>

<p>An ON CONFLICT clause may be specified as part of an UPDATE or INSERT
<i>trigger-step</i>. However if an ON CONFLICT clause is specified as part of 
the statement causing the trigger to fire, then this conflict handling
policy is used instead.</p>

<p>Triggers are automatically dropped when the table that they are 
associated with is dropped.</p>

<p>Triggers may be created on views, as well as ordinary tables. If one or
more INSERT, DELETE or UPDATE triggers are defined on a view, then it is not
an error to execute an INSERT, DELETE or UPDATE statement on the view, 
respectively. Thereafter, executing an INSERT, DELETE or UPDATE on the view
causes the associated triggers to fire. The real tables underlying the view
are not modified (except possibly explicitly, by a trigger program).</p>

<p><b>Example:</b></p>

<p>Assuming that customer records are stored in the "customers" table, and
that order records are stored in the "orders" table, the following trigger
ensures that all associated orders are redirected when a customer changes
his or her address:</p>
}
Example {
CREATE TRIGGER update_customer_address UPDATE OF address ON customers 
  BEGIN
    UPDATE orders SET address = new.address WHERE customer_name = old.name;
  END;
}
puts {
<p>With this trigger installed, executing the statement:</p>
}
Example {
UPDATE customers SET address = '1 Main St.' WHERE name = 'Jack Jones';
}
puts {
<p>causes the following to be automatically executed:</p>
}
Example {
UPDATE orders SET address = '1 Main St.' WHERE customer_name = 'Jack Jones';
}

Section {CREATE VIEW} {createview}

Syntax {sql-command} {
CREATE VIEW <view-name> AS <select-statement>
}

................................................................................
}

Section {DROP TABLE} droptable

Syntax {sql-command} {
DROP TABLE <table-name>
}

Section {DROP TRIGGER} droptrigger
Syntax {sql-statement} {
DROP TRIGGER <trigger-name>
}
puts { 
  <p>Used to drop a trigger from the database schema. Note that triggers
  are automatically dropped when the associated table is dropped.</p>
}

puts {
<p>The DROP TABLE statement consists of the keywords "DROP TABLE" followed
by the name of the table.  The table named is completely removed from
the disk.  The table can not be recovered.  All indices associated with
the table are also deleted.</p>}

................................................................................
In version 1.0 of SQLite, the VACUUM command would invoke 
<b>gdbm_reorganize()</b> to clean up the backend database file.
Beginning with version 2.0 of SQLite, GDBM is no longer used for
the database backend and VACUUM has become a no-op.
</p>
}





























puts {
































































































<p><hr /></p>
<p><a href="index.html"><img src="/goback.jpg" border=0 />
Back to the SQLite Home Page</a>
</p>

</body></html>}