Store boolean value in SQLite

Question

What is the type for a BOOL value in SQLite? I want to store in my table TRUE/FALSE values.

I could create a column of INTEGER and store in it values 0 or 1, but it won't be the best way to implement BOOL type.

Is there a way?

Answer 1

There is no native boolean data type for SQLite. Per the Datatypes doc:

SQLite does not have a separate Boolean storage class. Instead, Boolean values are stored as integers 0 (false) and 1 (true).

Answer 2

In SQLite the best you can do is use the integers 0 and 1 to represent false and true. You could declare the column type like this:

CREATE TABLE foo(mycolumn BOOLEAN NOT NULL CHECK (mycolumn IN (0, 1)));

Omit the NOT NULL if you want to allow NULL in addition to 0 and 1.

The use of the type name BOOLEAN here is for readability, to SQLite it's just a type with NUMERIC affinity.

Note that CHECK constraints have been supported since SQLite 3.3.0 (2006).

Here are some example INSERTs that will work: (note how strings and floating point numbers are parsed as integers)

sqlite> INSERT INTO foo VALUES(0);
sqlite> INSERT INTO foo VALUES(1);
sqlite> INSERT INTO foo VALUES(0.0);
sqlite> INSERT INTO foo VALUES(1.0);
sqlite> INSERT INTO foo VALUES("0.0");
sqlite> INSERT INTO foo VALUES("1.0");
sqlite> select mycolumn, typeof(mycolumn) from foo;
0|integer
1|integer
0|integer
1|integer
0|integer
1|integer

and some that will fail:

sqlite> INSERT INTO foo VALUES("-1");
Error: constraint failed
sqlite> INSERT INTO foo VALUES(0.24);
Error: constraint failed
sqlite> INSERT INTO foo VALUES(100);
Error: constraint failed
sqlite> INSERT INTO foo VALUES(NULL);
Error: foo.mycolumn may not be NULL
sqlite> INSERT INTO foo VALUES("true");
Error: constraint failed
sqlite> INSERT INTO foo VALUES("false");
Error: constraint failed

Answer 3

SQLite Boolean Datatype:
SQLite does not have a separate Boolean storage class. Instead, Boolean values are stored as integers 0 (false) and 1 (true).

You can convert boolean to int in this way:

int flag = (boolValue)? 1 : 0;

You can convert int back to boolean as follows:

 // Select COLUMN_NAME  values from db. 
 // This will be integer value, you can convert this int value back to Boolean as follows
Boolean flag2 = (intValue == 1)? true : false;

If you want to explore sqlite, here is a tutorial.
I have given one answer here. It is working for them.

Answer 4

using the Integer data type with values 0 and 1 is the fastest.

Answer 5

Further to ericwa's answer. CHECK constraints can enable a pseudo boolean column by enforcing a TEXT datatype and only allowing TRUE or FALSE case specific values e.g.

CREATE TABLE IF NOT EXISTS "boolean_test"
(
    "id" INTEGER PRIMARY KEY AUTOINCREMENT
,   "boolean" TEXT NOT NULL 
        CHECK( typeof("boolean") = "text" AND
               "boolean" IN ("TRUE","FALSE")
        )
);

INSERT INTO "boolean_test" ("boolean") VALUES ("TRUE");
INSERT INTO "boolean_test" ("boolean") VALUES ("FALSE");
INSERT INTO "boolean_test" ("boolean") VALUES ("TEST");

Error: CHECK constraint failed: boolean_test

INSERT INTO "boolean_test" ("boolean") VALUES ("true");

Error: CHECK constraint failed: boolean_test

INSERT INTO "boolean_test" ("boolean") VALUES ("false");

Error: CHECK constraint failed: boolean_test

INSERT INTO "boolean_test" ("boolean") VALUES (1);

Error: CHECK constraint failed: boolean_test

select * from boolean_test;

id  boolean
1   TRUE
2   FALSE

Answer 6

But,if you want to store a bunch of them you could bit-shift them and store them all as one int, a little like unix file permissions/modes.

For mode 755 for instance, each digit refers to a different class of users: owner, group, public. Within each digit 4 is read, 2 is write, 1 is execute so 7 is all of them like binary 111. 5 is read and execute so 101. Make up your own encoding scheme.

I'm just writing something for storing TV schedule data from Schedules Direct and I have the binary or yes/no fields: stereo, hdtv, new, ei, close captioned, dolby, sap in Spanish, season premiere. So 7 bits, or an integer with a maximum of 127. One character really.

A C example from what I'm working on now. has() is a function that returns 1 if the 2nd string is in the first one. inp is the input string to this function. misc is an unsigned char initialized to 0.

if (has(inp,"sap='Spanish'") > 0)
  misc += 1;
if (has(inp,"stereo='true'") > 0)
  misc +=2;
if (has(inp,"ei='true'") > 0)
  misc +=4;
if (has(inp,"closeCaptioned='true'") > 0)
  misc += 8;
if (has(inp,"dolby=") > 0)
  misc += 16;
if (has(inp,"new='true'") > 0)
  misc += 32;
if (has(inp,"premier_finale='") > 0)
  misc += 64;
if (has(inp,"hdtv='true'") > 0)
  misc += 128;

So I'm storing 7 booleans in one integer with room for more.

Answer 7

You could simplify the above equations using the following:

boolean flag = sqlInt != 0;

If the int representation (sqlInt) of the boolean is 0 (false), the boolean (flag) will be false, otherwise it will be true.

Concise code is always nicer to work with :)

Answer 8

Another way to do it is a TEXT column. And then convert the boolean value between Boolean and String before/after saving/reading the value from the database.

Ex. You have "boolValue = true;"

To String:

//convert to the string "TRUE"
string StringValue = boolValue.ToString;  

And back to boolean:

//convert the string back to boolean
bool Boolvalue = Convert.ToBoolean(StringValue);