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Sequences
author Adam Chlipala <adamc@hcoop.net>
date Sun, 07 Dec 2008 10:25:55 -0500
parents f31aa2a3a72d
children 8e615bb605c9
comparison
equal deleted inserted replaced
545:f31aa2a3a72d 546:7417c4b57aeb
1185 A $\mt{DELETE}$ command is formed from a table and a $\mt{WHERE}$ clause. 1185 A $\mt{DELETE}$ command is formed from a table and a $\mt{WHERE}$ clause.
1186 $$\begin{array}{l} 1186 $$\begin{array}{l}
1187 \mt{val} \; \mt{delete} : \mt{fields} ::: \{\mt{Type}\} \to \mt{sql\_table} \; \mt{fields} \to \mt{sql\_exp} \; [\mt{T} = \mt{fields}] \; [] \; [] \; \mt{bool} \to \mt{dml} 1187 \mt{val} \; \mt{delete} : \mt{fields} ::: \{\mt{Type}\} \to \mt{sql\_table} \; \mt{fields} \to \mt{sql\_exp} \; [\mt{T} = \mt{fields}] \; [] \; [] \; \mt{bool} \to \mt{dml}
1188 \end{array}$$ 1188 \end{array}$$
1189 1189
1190 \subsubsection{Sequences}
1191
1192 SQL sequences are counters with concurrency control, often used to assign unique IDs. Ur/Web supports them via a simple interface. The only way to create a sequence is with the $\mt{sequence}$ declaration form.
1193
1194 $$\begin{array}{l}
1195 \mt{type} \; \mt{sql\_sequence} \\
1196 \mt{val} \; \mt{nextval} : \mt{sql\_sequence} \to \mt{transaction} \; \mt{int}
1197 \end{array}$$
1198
1199
1190 \end{document} 1200 \end{document}