Convert multi-line if statment to single line with map

I suppose the real challenge is to have a map<> that compares the keys case-insensitively.

You do that by using a comparison predicate:

struct ci_less {
    bool operator()(std::string_view a, std::string_view b) const {
        return boost::lexicographical_compare(a, b, boost::is_iless{});
    }
};

You declare the map to use that predicate:

std::map<std::string, int, ci_less> const dataTypes {
    { "INT",      1 },
    { "BIGINT",   2 },
    { "uint8_t",  3 },
    { "uint16_t", 4 },
    { "LONG",     5 },
};

Note that it is now const, and I flipped the key/value pairs. See below

Some tests: Live On Coliru

// your sqlBufferTypes[i][j] e.g.:
for (std::string const key : { "uint32_t", "long", "lONg" }) {
    if (auto match = dataTypes.find(key); match != dataTypes.end()) {
        std::cout << std::quoted(key) << " maps to " << match->second;

        // more readable repeats lookup:
        std::cout << " or the same: " << dataTypes.at(key) << "\n"; // throws unless found
    } else {
        std::cout << std::quoted(key) << " not found\n";
    }
}

Prints

"uint32_t" not found
"long" maps to 5 or the same: 5
"lONg" maps to 5 or the same: 5

Flipping Key/Value

Dictionaries have a key field for lookup in all languages/libraries. So, to lookup in reverse you end up doing a linear search (just look at each element).

In Boost you can have your cake and eat it by defining a Multi Index Container.

Multi Index

This can facilitate lookup by multiple indices, including composite keys. (Search my answers for more real-life examples)

Live On Coliru

#include <boost/algorithm/string.hpp> // for is_iless et al.
#include <string_view>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <iostream> // for std::cout
#include <iomanip> // for std::quoted
#include <boost/locale.hpp>

namespace bmi = boost::multi_index;

struct ci_less {
    bool operator()(std::string_view a, std::string_view b) const {
        return boost::lexicographical_compare(a, b, boost::is_iless{});
    }
};

struct DbType {
    std::string_view name;
    int type_id;

    friend std::ostream& operator<<(std::ostream& os, DbType const& t) {
        return os << "DbType{" << std::quoted(t.name) << ", " << t.type_id << "}";
    }
};

using Map = bmi::multi_index_container<
    DbType,
    bmi::indexed_by<
        bmi::ordered_unique<
            bmi::tag<struct by_id>,
            bmi::member<DbType, int, &DbType::type_id> >,
        bmi::ordered_unique<
            bmi::tag<struct by_name>,
            bmi::member<DbType, std::string_view, &DbType::name>, ci_less>
    >
>;

int main() {

    Map dataTypes {
        { "INT",      1 },
        { "BIGINT",   2 },
        { "uint8_t",  3 },
        { "uint16_t", 4 },
        { "LONG",     5 },
    };

    auto& idx = dataTypes.get<by_name>();

    // your sqlBufferTypes[i][j] e.g.:
    for (std::string_view const key : { "uint32_t", "long", "lONg" }) {
        if (auto match = idx.find(key); match != idx.end()) {
            std::cout << std::quoted(key) << " -> " << *match << std::endl;
        } else {
            std::cout << std::quoted(key) << " not found\n";
        }
    }
}

Prints

"uint32_t" not found
"long" -> DbType{"LONG", 5}
"lONg" -> DbType{"LONG", 5}

Bimaps

Boost Bimap is a specialization of that for maps. It has fewer options, and notably adds operator[] style interface back.

using Map = boost::bimap<
    int,
    boost::bimaps::set_of<std::string_view, ci_less>>;

Sadly the constructor doesn't support initializaer lists, but we can use the iterator interface, and then we use the right view of the bimap to do lookups by name:

Live On Coliru

static const Map::relation s_mappings[] = {
    { 1, "INT" },
    { 2, "BIGINT" },
    { 3, "uint8_t" },
    { 4, "uint16_t" },
    { 5, "LONG" },
};

Map const dataTypes { std::begin(s_mappings), std::end(s_mappings) };

// your sqlBufferTypes[i][j] e.g.:
auto& vw = dataTypes.right;
for (std::string_view const key : { "uint32_t", "long", "lONg" }) {
    if (auto match = vw.find(key); match != vw.end()) {
        std::cout << std::quoted(key) << " -> " << match->second << "\n";
    } else {
        std::cout << std::quoted(key) << " not found\n";
    }
}

Prints

"uint32_t" not found
"long" -> 5
"lONg" -> 5