Mercurial > urweb
comparison doc/manual.tex @ 549:39282473d38f
Query syntax
| author | Adam Chlipala <adamc@hcoop.net> |
|---|---|
| date | Sun, 07 Dec 2008 12:02:54 -0500 |
| parents | 8e615bb605c9 |
| children | 11e150300ba0 |
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| 548:b3b06fef7bb5 | 549:39282473d38f |
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| 1243 One last useful function is for aborting any page generation, returning some XML as an error message. This function takes the place of some uses of a general exception mechanism. | 1243 One last useful function is for aborting any page generation, returning some XML as an error message. This function takes the place of some uses of a general exception mechanism. |
| 1244 $$\begin{array}{l} | 1244 $$\begin{array}{l} |
| 1245 \mt{val} \; \mt{error} : \mt{t} ::: \mt{Type} \to \mt{xml} \; [\mt{Body}] \; [] \; [] \to \mt{t} | 1245 \mt{val} \; \mt{error} : \mt{t} ::: \mt{Type} \to \mt{xml} \; [\mt{Body}] \; [] \; [] \to \mt{t} |
| 1246 \end{array}$$ | 1246 \end{array}$$ |
| 1247 | 1247 |
| 1248 | |
| 1249 \section{Ur/Web Syntax Extensions} | |
| 1250 | |
| 1251 Ur/Web features some syntactic shorthands for building values using the functions from the last section. This section sketches the grammar of those extensions. We write spans of syntax inside brackets to indicate that they are optional. | |
| 1252 | |
| 1253 \subsection{SQL} | |
| 1254 | |
| 1255 \subsubsection{Queries} | |
| 1256 | |
| 1257 $$\begin{array}{rrcll} | |
| 1258 \textrm{Queries} & Q &::=& (q \; [\mt{ORDER} \; \mt{BY} \; (E \; [D],)^+] \; [\mt{LIMIT} \; N] \; [\mt{OFFSET} \; N]) \\ | |
| 1259 \textrm{Pre-queries} & q &::=& \mt{SELECT} \; P \; \mt{FROM} \; T,^+ \; [\mt{WHERE} \; E] \; [\mt{GROUP} \; \mt{BY} \; p,^+] \; [\mt{HAVING} \; E] \\ | |
| 1260 &&& \mid q \; R \; q \\ | |
| 1261 \textrm{Relational operators} & R &::=& \mt{UNION} \mid \mt{INTERSECT} \mid \mt{EXCEPT} | |
| 1262 \end{array}$$ | |
| 1263 | |
| 1264 $$\begin{array}{rrcll} | |
| 1265 \textrm{Projections} & P &::=& \ast & \textrm{all columns} \\ | |
| 1266 &&& p,^+ & \textrm{particular columns} \\ | |
| 1267 \textrm{Pre-projections} & p &::=& t.f & \textrm{one column from a table} \\ | |
| 1268 &&& t.\{\{c\}\} & \textrm{a record of colums from a table (of kind $\{\mt{Type}\}$)} \\ | |
| 1269 \textrm{Table names} & t &::=& x & \textrm{constant table name (automatically capitalized)} \\ | |
| 1270 &&& X & \textrm{constant table name} \\ | |
| 1271 &&& \{\{c\}\} & \textrm{computed table name (of kind $\mt{Name}$)} \\ | |
| 1272 \textrm{Column names} & f &::=& X & \textrm{constant column name} \\ | |
| 1273 &&& \{c\} & \textrm{computed column name (of kind $\mt{Name}$)} \\ | |
| 1274 \textrm{Tables} & T &::=& x & \textrm{table variable, named locally by its own capitalization} \\ | |
| 1275 &&& x \; \mt{AS} \; t & \textrm{table variable, with local name} \\ | |
| 1276 &&& \{\{e\}\} \; \mt{AS} \; t & \textrm{computed table expression, with local name} \\ | |
| 1277 \textrm{SQL expressions} & E &::=& p & \textrm{column references} \\ | |
| 1278 &&& X & \textrm{named expression references} \\ | |
| 1279 &&& \{\{e\}\} & \textrm{injected native Ur expressions} \\ | |
| 1280 &&& \{e\} & \textrm{computed expressions, probably using $\mt{sql\_exp}$ directly} \\ | |
| 1281 &&& \mt{TRUE} \mid \mt{FALSE} & \textrm{boolean constants} \\ | |
| 1282 &&& \ell & \textrm{primitive type literals} \\ | |
| 1283 &&& \mt{NULL} & \textrm{null value (injection of $\mt{None}$)} \\ | |
| 1284 &&& E \; \mt{IS} \; \mt{NULL} & \textrm{nullness test} \\ | |
| 1285 &&& n & \textrm{nullary operators} \\ | |
| 1286 &&& u \; E & \textrm{unary operators} \\ | |
| 1287 &&& E \; b \; E & \textrm{binary operators} \\ | |
| 1288 &&& \mt{COUNT}(\ast) & \textrm{count number of rows} \\ | |
| 1289 &&& a(E) & \textrm{other aggregate function} \\ | |
| 1290 &&& (E) & \textrm{explicit precedence} \\ | |
| 1291 \textrm{Nullary operators} & n &::=& \mt{CURRENT\_TIMESTAMP} \\ | |
| 1292 \textrm{Unary operators} & u &::=& \mt{NOT} \\ | |
| 1293 \textrm{Binary operators} & b &::=& \mt{AND} \mid \mt{OR} \mid \neq \mid < \mid \leq \mid > \mid \geq \\ | |
| 1294 \textrm{Aggregate functions} & a &::=& \mt{AVG} \mid \mt{SUM} \mid \mt{MIN} \mid \mt{MAX} \\ | |
| 1295 \textrm{Directions} & D &::=& \mt{ASC} \mid \mt{DESC} \\ | |
| 1296 \textrm{SQL integer} & N &::=& n \mid \{e\} \\ | |
| 1297 \end{array}$$ | |
| 1298 | |
| 1299 Additionally, an SQL expression may be inserted into normal Ur code with the syntax $(\mt{SQL} \; E)$ or $(\mt{WHERE} \; E)$. | |
| 1300 | |
| 1301 | |
| 1248 \end{document} | 1302 \end{document} |