Documentation Source Text: Changes On Branch window-functions

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Changes In Branch window-functions Excluding Merge-Ins

This is equivalent to a diff from bf3c223723 to 783032878d

2019-03-26
13:11		Update window functions documentation. (check-in: bdc2a67078 user: dan tags: trunk)
2019-03-25
20:56		Updates to the change log for 3.28.0. (check-in: 32b82e8386 user: drh tags: trunk)
20:49		Update documentation to match the proposed window function changes. (Closed-Leaf check-in: 783032878d user: dan tags: window-functions)
15:19		Update the CLI documentation to describe the new --insert option to ".archive" and the behavior change to the --update option. (check-in: bf3c223723 user: drh tags: trunk)
14:30		Fix a documentation error: The preprocessor macro is SQLITE_HAVE_ZLIB, not SQLITE_USE_ZLIB. However the USE_ZLIB=1 option is what Makefile.msc expects. (check-in: 85f5f65d9f user: drh tags: trunk)

Changes to art/syntax/all-bnf.html.

Changes to art/syntax/all-text.html.

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Changes to art/syntax/bubble-generator-data.tcl.

Changes to art/syntax/frame-spec.gif.

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Changes to art/syntax/window-defn.gif.

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Changes to pages/windowfunctions.in.

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11 12 13 14 15 16 17 ~~18 19 20~~ 21 22 23 24 25 26 27	<tcl> RecursiveBubbleDiagram window-function-invocation window-defn frame-spec filter </tcl> <p>Window functions are distinguished from ordinary SQL functions by the presence of an OVER clause. If a function invocation has an OVER clause then it is a window function~~, and~~ if lacks an OVER clause it is an ~~ordinary~~ function. Window functions m~~ight also~~ have a FILTER clause in between the function and the OVER clause. <p>Unlike ordinary functions, window functions cannot use the DISTINCT keyword. Also, Window functions may only appear in the result set and in the ORDER BY clause of a SELECT statement.	\| \| \|	11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27	<tcl> RecursiveBubbleDiagram window-function-invocation window-defn frame-spec filter </tcl> <p>Window functions are distinguished from ordinary SQL functions by the presence of an OVER clause. If a function invocation has an OVER clause, then it is a window function. If it lacks an OVER clause, then it is an ordinary aggregate or scalar function. Window functions may have a FILTER clause in between the function and the OVER clause. <p>Unlike ordinary functions, window functions cannot use the DISTINCT keyword. Also, Window functions may only appear in the result set and in the ORDER BY clause of a SELECT statement.
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159 160 161 162 163 164 165 ~~166 167 168~~ 169 170 171 172 173 174 175 176 ~~177~~ 178 179 180 181 182 183 ~~184 185 186~~ 187 188 189 190 191 192 193 194 ~~195~~ ~~196~~ ~~197~~ ~~198 199 200 201~~ 202 ~~203 204 205 206~~ 207 208 209 210 211 212 213	</tcl> <p> The <yynonterm>frame-spec</yynonterm> determines which output rows are read by an aggregate window function. The <yynonterm>frame-spec</yynonterm> consists of three parts: <ul> ~~<li> A frame type - either RANGE or ~~ROWS.~~ <li> A starting frame boundary, ~~and~~ <li> An ending frame boundary.~~ </ul> <p>The ending frame boundary can be omitted, in which case it defaults to CURRENT ROW. <p>The default <yynonterm>frame-spec</yynonterm> is: <codeblock> ~~RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW~~ </codeblock> <p>The default means that aggregate window functions read all rows from the beginning of the partition up to and including the current row and its peers. <p> If the frame type is RANGE, then rows with the same values for ~~all ORDER BY~~ expressions are considered "peers". Or, if there are no ORDER BY ~~terms,~~ all rows are peers. Rows that are peers always have the same window ~~frames.~~ <p> There are five options for frame boundaries: <table striped=1> <tr><th>Frame Boundary <th>Description <tr><td>UNBOUNDED PRECEDING <td> The start of the frame is the first row in the set. <tr><td><expr> PRECEDING <td> <expr> is a constant expression ~~that evaluates to a non-negative ~~integ~~er value. The ~~start~~~~ ~~or end of the frame is <expr> rows ~~before the current row. "0~~~~ ~~PRECEDING" is the same as "CURRENT ~~ROW". This frame boundary type may~~~~ ~~only be used with ROWS frames.~~ <tr><td>CURRENT ROW <td> The current row. For RANGE frame types, all ~~peers of~~ the current row are also included in the window frame, ~~regardless of~~ whether CURRENT ROW is used as the starting or ending ~~frame boundary.~~ <tr><td><expr> FOLLOWING <td> <expr> is a constant expression that must evaluate to a non-negative ~~integ~~er value. The ~~start~~ or ~~end of~~ t~~he frame is~~ <expr> ~~rows after the current row~~. "0 ~~FOLLOWING" is the same as "CURRENT ROW". This frame boundary type may~~ ~~only be used with ROWS frames.~~ <tr><td>UNBOUNDED FOLLOWING <td> The end of the frame is the last row in the set. </table> <p> The ending frame boundary must not take a form that appears higher in the above list than the starting frame boundary.	\| \| \| > \| \| \| \| > \| > > \| > > > \| > > > > > > > > > > > > > > > > > > > > > > \| \| \| \| > \| \| < <	159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241	</tcl> <p> The <yynonterm>frame-spec</yynonterm> determines which output rows are read by an aggregate window function. The <yynonterm>frame-spec</yynonterm> consists of three parts: <ul> <li> A frame type - either ROWS, RANGE or GROUPS, <li> A starting frame boundary, <li> An ending frame boundary, <li> An EXCLUDE clause. </ul> <p>The ending frame boundary can be omitted, in which case it defaults to CURRENT ROW. <p>The default <yynonterm>frame-spec</yynonterm> is: <codeblock> RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW EXCLUDE NO OTHERS </codeblock> <p>The default means that aggregate window functions read all rows from the beginning of the partition up to and including the current row and its peers. <p> If the frame type is RANGE or GROUPS, then rows with the same values for all ORDER BY expressions are considered "peers". Or, if there are no ORDER BY terms, all rows are peers. Rows that are peers always have the same window frames. <p> There are five options for frame boundaries: <table striped=1> <tr><th>Frame Boundary <th>Description <tr><td>UNBOUNDED PRECEDING <td> The start of the frame is the first row in the set. <tr><td><expr> PRECEDING <td> <expr> is a constant expression that evaluates to a non-negative numeric value. If the frame type is ROWS or GROUPS, the expression must evaluate to an integer value.<br><br> For a ROWS frame, the start or end of the frame is <expr> rows before the current row.<br><br> For a GROUPS frame, the frame begins or ends with the peers <expr> groups of peers before or after the current row's group. For both ROWS and GROUPS frames, "0 PRECEDING" is the same as "CURRENT ROW". <br><br> A RANGE frame that uses "<expr> PRECEDING" must be paired with an ORDER BY clause that contains a single expression. If the ORDER BY expression for the current row is not a numeric value, then "<expr> PRECEDING" is equivalent to "CURRENT ROW". Otherwise, if the ORDER BY value is numeric for the current row, then the value of "<expr>" is used as a logical range for determining which groups are part of the current frame. <br><br> For example, if the ORDER BY clause is ASC (not DESC) and the "<expr> PRECEDING" is used as the start of the frame, then the first group in the frame is that with the smallest value for the ORDER BY expression that is greater than (current-row - <expr>). If the ORDER BY clause is DESC, then the first group is that with an ORDER BY expresion greater than (current-row + <expr>). <br><br> Or, if it is used as the end of the frame and the ORDER BY is ASC, then the last group in the grame is that with the largest value for the ORDER BY expression that is less than (current-row - <expr>). For DESC the last group is that with the smallest ORDER BY value that is greater than (current-row + <expr>). <tr><td>CURRENT ROW <td> The current row. For RANGE and GROUPS frame types, all peers of the current row are also included in the window frame, regardless of whether CURRENT ROW is used as the starting or ending frame boundary. <tr><td><expr> FOLLOWING <td> <expr> is a constant expression that must evaluate to a non-negative numeric value. It is handled in similarly to "<expr> PRECEDING". <tr><td>UNBOUNDED FOLLOWING <td> The end of the frame is the last row in the set. </table> <p> The ending frame boundary must not take a form that appears higher in the above list than the starting frame boundary.
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229 230 231 232 233 234 235 236 237 238 239 240 241 242	<i>-- two \| 5 \| E \| E </i> <i>-- </i> SELECT c, a, b, group_concat(b, '.') OVER ( ORDER BY c, a ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING ) AS group_concat FROM t1 ORDER BY c, a; </codeblock> <h2>The PARTITION BY Clause</h2> <p> A <yynonterm>window-defn</yynonterm> may include a PARTITION BY clause. If so, the rows returned by the SELECT statement are divided into groups - partitions - with the same values for each PARTITION BY expression, and then window-function processing is performed separately for each	> > > >	257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274	<i>-- two \| 5 \| E \| E </i> <i>-- </i> SELECT c, a, b, group_concat(b, '.') OVER ( ORDER BY c, a ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING ) AS group_concat FROM t1 ORDER BY c, a; </codeblock> <p> Even though they are technically part of the frame-specification, [exclude clause\|the EXCLUDE clause] and [window chaining] are described separately below. <h2>The PARTITION BY Clause</h2> <p> A <yynonterm>window-defn</yynonterm> may include a PARTITION BY clause. If so, the rows returned by the SELECT statement are divided into groups - partitions - with the same values for each PARTITION BY expression, and then window-function processing is performed separately for each
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289 290 291 292 293 294 295 296 297 298 299 300 301 302	<i>-- one \| 7 \| G \| A.C.D.F.G </i> <i>-- </i> SELECT c, a, b, group_concat(b, '.') FILTER (WHERE c!='two') OVER ( ORDER BY a ) AS group_concat FROM t1 ORDER BY a; </codeblock> <h1>Built-in Window Functions</h1> <p> As well as aggregate window functions, SQLite features a set of built-in window functions based on <a href=https://www.postgresql.org/docs/10/static/functions-window.html> those supported by PostgreSQL</a>.	> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >	321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427	<i>-- one \| 7 \| G \| A.C.D.F.G </i> <i>-- </i> SELECT c, a, b, group_concat(b, '.') FILTER (WHERE c!='two') OVER ( ORDER BY a ) AS group_concat FROM t1 ORDER BY a; </codeblock> <h2 tags="exclude clause">The EXCLUDE Clause</h2> <p> The optional EXCLUDE clause may take any of the following four forms: <ul> <li> <p><b> EXCLUDE NO OTHERS</b>: This is the default. In this case no rows are excluded from the window frame as defined by its starting and ending frame boundaries. <li> <p><b> EXCLUDE CURRENT ROW</b>: In this case the current row is excluded from the window frame. <li> <p><b> EXCLUDE GROUP</b>: In this case the current row and all other rows that are peers of the current row are excluded from the group. When processing an EXCLUDE clause, all rows with the same ORDER BY values, or all rows in the partition if there is no ORDER BY clause, are considered peers, even if the frame type is ROWS. <li> <p><b> EXCLUDE TIES</b>: In this case the current row is part of the frame, but all other peers are excluded. </ul> <codeblock> <i>-- The following SELECT statement returns:</i> <i>-- </i> <i>-- c \| a \| b \| no_others \| current_row \| grp \| ties</i> <i>-- one \| 1 \| A \| A.D.G \| D.G \| \| A</i> <i>-- one \| 4 \| D \| A.D.G \| A.G \| \| D</i> <i>-- one \| 7 \| G \| A.D.G \| A.D \| \| G</i> <i>-- three \| 3 \| C \| A.D.G.C.F \| A.D.G.F \| A.D.G \| A.D.G.C</i> <i>-- three \| 6 \| F \| A.D.G.C.F \| A.D.G.C \| A.D.G \| A.D.G.F</i> <i>-- two \| 2 \| B \| A.D.G.C.F.B.E \| A.D.G.C.F.E \| A.D.G.C.F \| A.D.G.C.F.B</i> <i>-- two \| 5 \| E \| A.D.G.C.F.B.E \| A.D.G.C.F.B \| A.D.G.C.F \| A.D.G.C.F.E</i> <i>-- </i> SELECT c, a, b, group_concat(b, '.') OVER ( ORDER BY c GROUPS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW EXCLUDE NO OTHERS ) AS no_others, group_concat(b, '.') OVER ( ORDER BY c GROUPS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW EXCLUDE CURRENT ROW ) AS current_row, group_concat(b, '.') OVER ( ORDER BY c GROUPS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW EXCLUDE GROUP ) AS grp, group_concat(b, '.') OVER ( ORDER BY c GROUPS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW EXCLUDE TIES ) AS ties FROM t1 ORDER BY c, a; </codeblock> <h2 tags="window chaining">Window Chaining</h2> <p> Window chaining is a shorthand that allows one window to be defined in terms of another. Specifically, the shorthand allows the new window to implicitly copy the PARTITION BY and optionally ORDER BY clauses of the base window. For example, in the following: <codeblock> SELECT group_concat(b, '.') OVER ( win ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW ) FROM t1 WINDOW win AS (PARTITION BY a ORDER BY c) </codeblock> <p> the window used by the group_concat() is equivalent to "PARTITION BY a ORDER BY c ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW". In order to use window chaining, all of the following must be true: <ul> <li><p>The new window definition must not include a PARTITION BY clause. The PARTITION BY clause, or lack thereof, is always copied from the base window. <li><p>If the base window has an ORDER BY clause, it is copied into the new window. In this case the new window must not specify an ORDER BY clause. If the base window has no ORDER BY clause, one may be specified as part of the new window definition. <li><p>The base window may not specify a frame specification. </ul> <p>The two fragments of SQL below are similar, but not entirely equivalent, as the latter will fail if the definition of window "win" contains a frame specification. <codeblock> SELECT group_concat(b, '.') OVER win ... SELECT group_concat(b, '.') OVER (win) ... </codeblock> <h1>Built-in Window Functions</h1> <p> As well as aggregate window functions, SQLite features a set of built-in window functions based on <a href=https://www.postgresql.org/docs/10/static/functions-window.html> those supported by PostgreSQL</a>.
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