51 lines
1.3 KiB
C
51 lines
1.3 KiB
C
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/**
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* @file mix_cc/sql/select.h
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* @brief 查询语句
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* @author Cat (null.null.null@qq.com)
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* @version 0.1
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* @date 2021-09-17
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*
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* Copyright: Baosight Co. Ltd.
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* DO NOT COPY/USE WITHOUT PERMISSION
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*
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*/
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#pragma once
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#include <mix_cc/sql/public.h>
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#include <mix_cc/sql/from.h>
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#include <mix_cc/sql/column.h>
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#include <mix_cc/sql/statement.h>
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#include <algorithm>
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namespace mix_cc {
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namespace sql {
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template <typename... Columns>
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struct select_t : public prev_statement_t<void>, public statement_t {
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static constexpr auto s_text = op::cmd_t::select;
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constexpr explicit select_t(Columns... columns)
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: prev_statement_t<void>(), cols_(hana::make_tuple(columns...)) {}
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template <typename Tab>
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constexpr auto from(Tab tab) {
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return from_t(*this, tab);
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}
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constexpr auto get_command() {
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auto sel_str_c = s_text + " "_s;
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auto col_names =
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hana::transform(cols_, [](auto col) { return col.col_name; });
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auto r_str_c = hana::fold_left(
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col_names, [](auto col1, auto col2) { return col1 + ","_s + col2; });
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return sel_str_c + r_str_c;
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}
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public:
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hana::tuple<Columns...> cols_;
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};
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template <typename... Columns>
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auto select(Columns... columns) {
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return select_t<Columns...>(columns...);
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}
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} // namespace sql
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} // namespace mix_cc
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