Compilable SQL

Concept of SQL generation using common C++ syntax and power of compiler's data types checking.

1. Create a table

The given table with 6 columns

[ ID | C1 | C2 | C3 | C4 | C5 ]
[----|----|----|----|----|----]

Where:

• ID - it is unique autoicremented row IDs (PRIMARY_KEY, AUTOINCREMENT)
• C1 - floating point data with defaul value 3.14
• C2 - timestamp with non-null values
• C3 - string with default value "" (empty string)
• C4 - floating point rows with default value 5.65
• C5 - floating point rows without any extra parameters

Can be created with SQL:

CREATE TABLE Table1
(
    ID INTEGER PRIMARY KEY AUTOINCREMENT,
    C1 REAL DEFAULT 3.140000,
    C2 DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
    C3 TEXT DEFAULT '',
    C4 REAL DEFAULT 5.650000,
    C5 REAL
);

This SQL request can be generated with given C++ snippet:

1. Declate table as a reqular structure:

struct Table1: Table
{
    TableColumn<int>          ID = { SqlName("ID"), TCS(TCS::PRIMARY_KEY|TCS::AUTOINCREMENT) };
    TableColumn<double>       C1 = { SqlName("C1"), TCS::DEFAULT, 3.14 };
    TableColumn<std::time_t>  C2 = { SqlName("C2"), TCS(TCS::DEFAULT|TCS::NOT_NULL) };
    TableColumn<std::string>  C3 = { TCS::DEFAULT };
    TableColumn<float>        C4 = { 5.65f };
    TableColumn<float>        C5;

    Table1 (): Table(SqlName("Table1")) { registerColumns(ID, C1, C2, C3, C4, C5); }
};

2. Create instance of Table1 and call method to generate needed SQL request:

Table1 table1;
std::string sql = table1.getSqlTableCreate();

2. Data row insertion

To add two rows with given values:

[ ID | C1   | C2         | C3    | C4   | C5    ]
[----|------|------------|-------|------|-------]
[ 0  | 1.23 | 1631730839 | "XXX" | 3.14 | 31.4  ]
[ 1  | 45.6 | 1631730839 | "YYY" | 56.7 | 8.88  ]
[----|------|------------|-------|------|-------]

Need SQL request:

INSERT INTO Table1 ( C1, C2, C3, C4, C5 ) VALUES ( 1.23, 1631730839, 'XXX', 3.140000, 31.4 );
INSERT INTO Table1 ( C1, C2, C3, C4, C5 ) VALUES ( 45.6, 1631730839, 'YYY', 56.7, 8.88 );

Can be generated by CSQL:

table1.addRow(0, 1.23, time(0), "XXX", 3.14f, 31.4f);
table1.addRow(0, 1.11, time(0), "YYY", 3.13f, 8.88f);

std::string sql = Table1.getSqlRowsInsert();

The compiler will check, that data passed in addRow fits data types of appopriate columns (fields of Table1 structure).

3. Data selection

3.1. Simple selection

To simply select some specific data needed given SQL:

SELECT ID, C1, C2
FROM table1

Can be generated by CSQL:

std::cout << table1.getSqlRowsSelect
(
    /* list of columns to select */ { table1.ID, table1.C1, table1.C2 },
);

3.2. Selection with conditions

To select some specific data with needed conditions it can be used given SQL:

SELECT ID, C1, C2
FROM table1
WHERE C1 = 3.14 AND C2 > C3 AND C4 IN ( ...some_nested_condition_ )

Can be generated by CSQL:

std::cout << table1.getSqlRowsSelect
(
    { table1.ID, table1.C1, table1.C2 },
    /* "WHERE" condition */ ( table1.C1 ==  3.14 && table1.C2 > table1.C3 && table1.C4.IN( table2.getSqlRowsSelect() ) ),
);

It has a common C-like style with values data type checking and nesting conditions support.

3.3. Ordering, limit and top offset

To order selected rows, limit and offset it can be used given SQL:

SELECT ID, C1, C2
FROM table1
WHERE C1 = 3.14 AND C2 > C3 AND C4 IN ( ...some_nested_condition_ )
ORDER BY C1, C2 ASC, C3 DESC
LIMIT 300
TOP 25

Can be generated by CSQL:

std::cout << table1.getSqlRowsSelect
(
    { table1.ID, table1.C1, table1.C2 },
    ( table1.C1 ==  3.14 && table1.C2 > table1.C3 && table1.C4.IN( table2.getSqlRowsSelect() ) ),
    /* Ordering parameters       */ { { table1.C1, TRST::DEF  }, { table1.C2, TRST::ASC  }, { table1.C3, TRST::DESC } },
    /* LIMIT selected rows count */ 300,
    /* TOP offset                */ 25
);

4. CSQL SQLite

There is library CSQL-SQLite that manages data in SQLite database. Example of using can be found in tests of libcsql-sqlite and in demo src/main.cpp.

5. Links

• More examples can be found:

  • in demo src/main.cpp (usage of SQLite3)
  • in tests of both of the libraries libcsql and libcsql-sqlite.

• Project uses CppProjectTemplate_VSCodeCMakeTools

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