| JSON | PATH | -> operator (all) | ->> operator (MySQL/PG) + | ->> operator (SQLite) | json_extract() (SQLite) + |
|---|---|---|---|---|---|
| **'{"a":123}'** | '$.a' | **'123'** | '123' | 123 | 123 + |
| **'{"a":4.5}'** | '$.a' | **'4.5'** | '4.5' | 4.5 | 4.5 + |
| **'{"a":"xyz"}'** | '$.a' | **'"xyz"'** | 'xyz' | 'xyz' | 'xyz' + |
| **'{"a":null}'** | '$.a' | **'null'** | NULL | NULL | NULL + |
| **'{"a":[6,7,8]}'** | '$.a' | **'[6,7,8]'** | '[6,7,8]' | '[6,7,8]' | **'[6,7,8]'** + |
| **'{"a":{"x":9}}'** | '$.a' | **'{"x":9}'** | '{"x":9}' | '{"x":9}' | **'{"x":9}'** + |
| **'{"b":999}'** | '$.a' | NULL | NULL | NULL | NULL + |
| SQL expression | Works in MySQL? | Works in PG? | Works in SQLite + |
|---|---|---|---|
| value1->'$.a' | yes | no | yes + |
| value1->'a' | no | yes | yes + |
| value2->'$[2]' | yes | no | yes + |
| value2->2 | no | yes | yes + |
| TEXT | BLOB | No change ** |
| BLOB | INTEGER | [CAST] to INTEGER ** |
| BLOB | FLOAT | [CAST] to REAL -** |
| BLOB | TEXT | Add a zero terminator if needed +** |
| BLOB | TEXT | [CAST] to TEXT, ensure zero terminator ** |
If the constraint comes from a WHERE clause expression that contains +** a [COLLATE operator], then the name of the collation specified by +** that COLLATE operator is returned. +**
If there is no COLLATE operator, but the column that is the subject +** of the constraint specifies an alternative collating sequence via +** a [COLLATE clause] on the column definition within the CREATE TABLE +** statement that was passed into [sqlite3_declare_vtab()], then the +** name of that alternative collating sequence is returned. +**
Otherwise, "BINARY" is returned. +**
+** ^If the sqlite3_vtab_distinct() interface returns 0, that means +** that the query planner needs the virtual table to return all rows in the +** sort order defined by the "nOrderBy" and "aOrderBy" fields of the +** [sqlite3_index_info] object. This is the default expectation. If the +** virtual table outputs all rows in sorted order, then it is always safe for +** the xBestIndex method to set the "orderByConsumed" flag, regardless of +** the return value from sqlite3_vtab_distinct(). +**
+** ^(If the sqlite3_vtab_distinct() interface returns 1, that means +** that the query planner does not need the rows to be returned in sorted order +** as long as all rows with the same values in all columns identified by the +** "aOrderBy" field are adjacent.)^ This mode is used when the query planner +** is doing a GROUP BY. +**
+** ^(If the sqlite3_vtab_distinct() interface returns 2, that means +** that the query planner does not need the rows returned in any particular +** order, as long as rows with the same values in all "aOrderBy" columns +** are adjacent.)^ ^(Furthermore, only a single row for each particular +** combination of values in the columns identified by the "aOrderBy" field +** needs to be returned.)^ ^It is always ok for two or more rows with the same +** values in all "aOrderBy" columns to be returned, as long as all such rows +** are adjacent. ^The virtual table may, if it chooses, omit extra rows +** that have the same value for all columns identified by "aOrderBy". +** ^However omitting the extra rows is optional. +** This mode is used for a DISTINCT query. +**
+** ^A call to sqlite3_vtab_in(P,N,-1) will return true (non-zero) +** if and only if the [sqlite3_index_info|P->aConstraint][N] constraint +** is an [IN operator] that can be processed all at once. ^In other words, +** sqlite3_vtab_in() with -1 in the third argument is a mechanism +** by which the virtual table can ask SQLite if all-at-once processing +** of the IN operator is even possible. +** +**
+** ^A call to sqlite3_vtab_in(P,N,F) with F==1 or F==0 indicates +** to SQLite that the virtual table does or does not want to process +** the IN operator all-at-once, respectively. ^Thus when the third +** parameter (F) is non-negative, this interface is the mechanism by +** which the virtual table tells SQLite how it wants to process the +** IN operator. +**
The P->aConstraintUsage[N].argvIndex value is set to a positive +** integer. This is how the virtual table tells SQLite that it wants to +** use the N-th constraint. +** +**
The last call to sqlite3_vtab_in(P,N,F) for which F was +** non-negative had F>=1. +**
+** for(rc=sqlite3_vtab_in_first(pList, &pVal);
+** rc==SQLITE_OK && pVal
+** rc=sqlite3_vtab_in_next(pList, &pVal)
+** ){
+** // do something with pVal
+** }
+** if( rc!=SQLITE_OK ){
+** // an error has occurred
+** }
+**