how to extract the today's date out of the date column using SQL query?

Question

I assume I would need to change query in order to sort the data with today's date.

Please tell me how to change it though...

SQL QUERY in ToDoDao

@Query("SELECT * FROM todo_table WHERE date(date) = date('now')")
fun getTodayList(): Flow<List<ToDoTask>>

DATABASE

@Entity(tableName = DATABASE_TABLE)
data class ToDoTask(
    @PrimaryKey(autoGenerate = true) val id: Int = 0,
    @ColumnInfo(name = "title") val title: String,
    @ColumnInfo(name = "description") val description: String,
    @ColumnInfo(name = "priority") val priority: Priority,
    @ColumnInfo(name = "date") val date: String,
    @ColumnInfo(name = "favorite") var favorite: Boolean)

date val in ViewModel class

val date : MutableState<String> = mutableStateOf("")

datas inserted enter image description here

I have tried the code below and I was able to activate the function as the query as I intented, so I think the query is the issue here.

@Query("SELECT * FROM todo_table WHERE date = '2023-2-14'")
fun getTodayList(): Flow<List<ToDoTask>>

Answer 1

The Issue

The issue is that the SQLite date function expects the date to be in an accepted format. YYYY-M-DD is not such a format and will result in null rather than a date. YYYY-MM-DD is an accepted format (see https://www.sqlite.org/lang_datefunc.html#time_values). That is leading zeros are used to expand single digit numbers to 2 digit numbers for the month and day of month values.

The Fix (not recommended)

To fix the issue you have shown, you could use (see the However below):-

@Query("SELECT * FROM todo_table WHERE date(substr(date,1,5)||CASE WHEN substr(date,7,1) = '-' THEN '0' ELSE '' END ||substr(date,6)) = date('now');")

If the month was 2 numerics i.e. MM (e.g. 02 for February) then the above would not be necessary.

The CASE WHEN THEN ELSE END construct is similar to IF THEN ELSE END. see https://www.sqlite.org/lang_expr.html#the_case_expression. This is used to add the additional leading 0, when omitted, to the string used by the date function.

However, the above would not cater for days that have the leading 0 omitted for the first 9 days of the month. This due to the 4 permutations of the format (YYYY-MM-DD, YYYY-MM-D, YYYY-M-D and YYYY-M-DD) would be more complex e.g.

@Query("SELECT * FROM todo_table WHERE date(CASE WHEN length(date) = 8 THEN substr(date,1,5)||'0'||substr(date,6,1)||'-0'||substr(date,8) WHEN length(date) = 9 AND substr(date,7,1) = '-' THEN substr(date,1,5)||'0'||substr(date,6) WHEN length(date) = 9 AND substr(date,8,1) = '-' THEN substr(date,1,8)||'0'||substr(date,9) ELSE date END) = date('now');")

Recommended Fix

The recommended fix is to store values using one of the accepted formats rather than try to manipulate values to be an accepted date to then be worked upon using the date and time functions.