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42 lines
1.9 KiB
Markdown
42 lines
1.9 KiB
Markdown
# New data types
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## optional
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Nullable values are represented as `std::optional` if you are using C++17 or later, `sqlpp::compat::optional` otherwise.
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## string_view
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Text results are represented as `std::string_view` if you are using C++17 or later, `sqlpp::compat::string_view` otherwise.
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# span<uint8_t>
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Blob results are represented as `std::span<uint8_t>` if you are using C++20 or later, `sqlpp::compat::span<uint8_t>` otherwise.
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# Result values
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Result rows are represented as structs with the respective columns represented as data members. In version 1.0, these data members used to have a type that wrapped the actual data and provided conversion operators and functions to check for NULL.
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Now data members have the correct data type, e.g. `int64_t` or `optional<string_view>`.
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# No read-only columns
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Version 1.0 had the concept of read-only columns, e.g. you could not modify a column with auto-increment values.
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This concept has been removed. In most cases, you will still not want to modify columns with auto-increment values, but you can do it now, if you want to.
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# IS DISCTINCT FROM
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Version 1.0 used to have `is_equal_to_or_null` which translated to either `=` or `IS NULL`. While useful, this did not work with parameters.
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The library now offers `is_distinct_from` and `is_not_distinct_from` which safely compares with actual values and `NULL`.
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# Selecting aggregate functions
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In version 1.0, many functions automatically came with a name. This was convenient for selecting, but also rather unspecific, e.g. `select(max(tab.price)).from(tab).unconditionally()` would yield rows with data member called `count_`.
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Now, functions do not come with names. While this will lead to lightly more code, the assumption is that this will lead to slightly more readable code, e.g.
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```
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SQLPP_ALIAS_PROVIDER(max_price);
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// ...
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for (const auto& row : db(select(max(tab.price)).from(tab).unconditionally()))
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{
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std::cout << row.max_price << '\n';
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}
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```
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